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Sample records for high-gradient srf cavity

  1. An update on the study of high-gradient elliptical SRF cavities at 805 MHz for proton and other applications

    Energy Technology Data Exchange (ETDEWEB)

    Tajima, Tsuyoshi [Los Alamos National Laboratory; Haynes, Brian [Los Alamos National Laboratory; Krawczyk, Frank [Los Alamos National Laboratory; Madrid, Mike [Los Alamos National Laboratory; Roybal, Ray [Los Alamos National Laboratory; Simakov, Evgenya [Los Alamos National Laboratory; Clemens, Bob [TJNAF; Macha, Jurt [TJNAF; Manus, Bob [TJNAF; Rimmer, Bob [TJNAF; Rimmer, Bob [TJNAF; Turlington, Larry [TJNAF

    2010-09-09

    An update on the study of 805 MHz elliptical SRF cavities that have been optimized for high gradient will be presented. An optimized cell shape, which is still appropriate for easy high pressure water rinsing, has been designed with the ratios of peak magnetic and electric fields to accelerating gradient being 3.75 mT/(MV/m) and 1.82, respectively. A total of 3 single-cell cavities have been fabricated. Two of the 3 cavities have been tested so far. The second cavity achieved an E{sub acc} of {approx}50 MV/m at Q{sub 0} of 1.4 x 10{sup 10}. This result demonstrates that 805 MHz cavities can, in principle, achieve as high as, or could even be better than, 1.3 GHz high-gradient cavities.

  2. CEBAF's SRF cavity manufacturing experience

    International Nuclear Information System (INIS)

    Benesch, J.F.; Reece, C.E.

    1994-01-01

    Construction of the Continuous Electron Beam Accelerator Facility (CEBAF) recirculating linac represents the largest scale application of superconducting rf (SRF) technology to date. The accelerating structures in CEBAF are 169 pairs of 1.5 GHz superconducting rf cavities -- 9 pairs in an injector and 80 pairs each in two linacs. The beam is to be recirculated up to five passes through each linac. Data is presented on mechanical tolerances achieved by the industrial fabricator of the rf cavities (Siemens). Liquid helium leak rates integrated over 22 vacuum seals have been measured on over 110 cavity pairs. A roughly normal distribution of the log 10 (leak rate) is seen, centered about a rate of 10 -10.4 torr-l/s. Over 140 pairs of the cavities have been assembled and have completed rf testing at 2.0 K. Among these, 54% demonstrated usable accelerating gradients greater than 10 MV/m. Although the rf performance characteristics well exceed the CEBAF baseline requirements of 5 MV/m at Q 0 = 2.4x10 9 , the usual limiting phenomena are encountered: field emission, quenching, and occasional multipacting. A discussion of the occurrence conditions and severity of these phenomena during production cavity testing is presented. The frequency with which performance is limited by quenching suggests that additional material advances may be required for applications which require the reliable achievement of accelerating gradients of more than 15 MV/m

  3. Fabrication of elliptical SRF cavities

    Science.gov (United States)

    Singer, W.

    2017-03-01

    The technological and metallurgical requirements of material for high-gradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10 μg g-1. The hydrogen content should be kept below 2 μg g-1 to prevent degradation of the quality factor (Q-value) under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Traditional and alternative cavity mechanical fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and electron beam welding. The welding of half-cells is a delicate procedure, requiring intermediate cleaning steps and a careful choice of weld parameters to achieve full penetration of the joints. A challenge for a welded construction is the tight mechanical and electrical tolerances. These can be maintained by a combination of mechanical and radio-frequency measurements on half-cells and by careful tracking of weld shrinkage. The main aspects of quality assurance and quality management are mentioned. The experiences of 800 cavities produced for the European XFEL are presented. Another cavity fabrication approach is slicing discs from the ingot and producing cavities by deep drawing and electron beam welding. Accelerating gradients at the level of 35-45 MV m-1 can be achieved by applying electrochemical polishing treatment. The single-crystal option (grain boundary free) is discussed. It seems that in this case, high performance can be achieved by a simplified treatment procedure. Fabrication of the elliptical resonators from a seamless pipe as an alternative is briefly described. This technology has yielded good

  4. Resonance control in SRF cavities at FNAL

    Energy Technology Data Exchange (ETDEWEB)

    Schappert, W.; Pischalnikov, Y.; /Fermilab; Scorrano, M.; /INFN, Pisa

    2011-03-01

    The Lorentz force can dynamically detune pulsed Superconducting RF cavities. Considerable additional RF power can be required to maintain the accelerating gradient if no effort is made to compensate for this detuning. Compensation systems using piezo actuators have been used successfully at DESY and elsewhere to control Lorentz Force Detuning (LFD). Recently, Fermilab has developed an adaptive compensation system for cavities in the Horizontal Test Stand, in the SRF Accelerator Test Facility, and for the proposed Project X.

  5. Development of high gradient superconducting radio frequency cavities for international linear collider and energy recovery linear accelerator

    International Nuclear Information System (INIS)

    Saito, Kenji; Furuta, Fumio; Saeki, Takayuki

    2009-01-01

    Superconducting radio frequency (SRF) cavities were used for storage rings like TRISTAN at KEK, HERA at DESY and LEP-II at CERN in 1990-2000. This technology has been accepted as a common accelerator technology. In August 2004, ITPR recommended an electron/positron linear collider based on SRF technology for the future high energy physics. ICFA accepted the recommendation and named it ILC (International Linear Collider). SRF cavities have a very unique feature due to its very small surface resistance. Energy recovery is another very exciting application. Many laboratories are proposing ERL (Energy Recovery LINAC) as a next bright photon source. In these accelerators, production of SRF cavities with reliably high performance is the most important issue. In this paper the activities of ILC high gradient cavities will be introduced. ERL activity will be briefly presented. (author)

  6. Development of High Gradient Superconducting Radio Frequency Cavities for International Linear Collider and Energy Recovery Linear Accelerator

    Science.gov (United States)

    Saito, Kenji; Furuta, Fumio; Saeki, Takayuki

    Superconducting radio frequency (SRF) cavities were used for storage rings like TRISTAN at KEK, HERA at DESY and LEP-II at CERN in 1990-2000. This technology has been accepted as a common accelerator technology. In August 2004, ITPR recommended an electron/positron linear collider based on SRF technology for the future high energy physics. ICFA accepted the recommendation and named it ILC (International Linear Collider). SRF cavities have a very unique feature due to its very small surface resistance. Energy recovery is another very exciting application. Many laboratories are proposing ERL (Energy Recovery LINAC) as a next bright photon source. In these accelerators, production of SRF cavities with reliably high performance is the most important issue. In this paper the activities of ILC high gradient cavities will be introduced. ERL activity will be briefly presented.

  7. SRF Cavity Fabrication and Materials

    CERN Document Server

    Singer, W

    2014-07-17

    The technological and metallurgical requirements of material for highgradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10μg/g. The hydrogen content should be kept below 2μg/g to prevent degradation of the Q-value under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Defects may be detected by quality control methods such as eddy current scanning and identified by a number of special methods. Conventional and alternative cavity fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and Electron-Beam Welding (EBW). The welding of half-cells is a delicate...

  8. SRF Cavity Fabrication and Materials

    Energy Technology Data Exchange (ETDEWEB)

    Singer, W [DESY (Germany)

    2014-07-01

    The technological and metallurgical requirements of material for highgradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10μg/g. The hydrogen content should be kept below 2μg/g to prevent degradation of the Q-value under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Defects may be detected by quality control methods such as eddy current scanning and identified by a number of special methods. Conventional and alternative cavity fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and Electron-Beam Welding (EBW). The welding of half-cells is a delicate procedure, requiring intermediate cleaning steps and a careful choice of weld parameters to achieve full penetration of the joints. The equator welds are particularly critical. A challenge for a welded construction is the tight mechanical and electrical tolerances. These can be maintained by a combination of mechanical and radio-frequency measurements on halfcells and by careful tracking of weld shrinkage. The established procedure is suitable for large series production. The main aspects of quality assurance management are mentioned. Another cavity fabrication approach is slicing discs from the ingot and producing cavities by deep drawing and EBW. Accelerating gradients at the level of 35–45 MV·m–1 can be achieved by applying Electropolishing (EP) treatment. Furthermore, the single-crystal option (grain boundary free) is promising. It seems that in this case, high performance can be achieved by a simplified treatment procedure. Fabrication of the

  9. Strategies for waveguide coupling for SRF cavities

    International Nuclear Information System (INIS)

    Doolittle, L.R.

    1998-01-01

    Despite widespread use of coaxial couplers in SRF cavities, a single, simple waveguide coupling can be used both to transmit generator power to a cavity, and to remove a large class of Higher Order Modes (HOMs, produced by the beam). There are balances and tradeoffs to be made, such as the coupling strength of the various frequencies, the transverse component of the coupler fields on the beam axis, and the magnitude of the surface fields and currents. This paper describes those design constraints, categories of solutions, and examples from the CEBAF Energy Upgrade studies

  10. Superconducting niobium cavities with high gradients

    International Nuclear Information System (INIS)

    Kneisel, P.; Saito, K.

    1992-01-01

    Present accelerator projects making use of superconducting cavity technology are constructed with design accelerating gradients E acc ranging between 5 MV/m and 8 MV/m and Q-values of several 10 9 . Future plans for upgrades of existing accelerators or for linear colliders call for gradients greater than 15 MV/m corresponding to peak surface electric fields above 30 MV/m. These demands challenge state-of-the-art production technology and require improvements in processing and handling of these cavities to overcome the major performance limitation of field emission loading. This paper reports on efforts to improve the performance of cavities made from niobium from different suppliers by using improved cleaning techniques after processing and ultrahigh vacuum annealing at temperatures of 1400 C. In single cell L-band cavities peak surface electric fields as high as 50 MV/m have been measured without significant field emission loading. (Author) 8 refs., fig

  11. Multipacting studies in elliptic SRF cavities

    Science.gov (United States)

    Prakash, Ram; Jana, Arup Ratan; Kumar, Vinit

    2017-09-01

    Multipacting is a resonant process, where the number of unwanted electrons resulting from a parasitic discharge rapidly grows to a larger value at some specific locations in a radio-frequency cavity. This results in a degradation of the cavity performance indicators (e.g. the quality factor Q and the maximum achievable accelerating gradient Eacc), and in the case of a superconducting radiofrequency (SRF) cavity, it leads to a quenching of superconductivity. Numerical simulations are essential to pre-empt the possibility of multipacting in SRF cavities, such that its design can be suitably refined to avoid this performance limiting phenomenon. Readily available computer codes (e.g.FishPact, MultiPac,CST-PICetc.) are widely used to simulate the phenomenon of multipacting in such cases. Most of the contemporary two dimensional (2D) codes such as FishPact, MultiPacetc. are unable to detect the multipacting in elliptic cavities because they use a simplistic secondary emission model, where it is assumed that all the secondary electrons are emitted with same energy. Some three-dimensional (3D) codes such as CST-PIC, which use a more realistic secondary emission model (Furman model) by following a probability distribution for the emission energy of secondary electrons, are able to correctly predict the occurrence of multipacting. These 3D codes however require large data handling and are slower than the 2D codes. In this paper, we report a detailed analysis of the multipacting phenomenon in elliptic SRF cavities and development of a 2D code to numerically simulate this phenomenon by employing the Furman model to simulate the secondary emission process. Since our code is 2D, it is faster than the 3D codes. It is however as accurate as the contemporary 3D codes since it uses the Furman model for secondary emission. We have also explored the possibility to further simplify the Furman model, which enables us to quickly estimate the growth rate of multipacting without

  12. HOM frequency control of SRF cavity in high current ERLs

    Science.gov (United States)

    Xu, Chen; Ben-Zvi, Ilan

    2018-03-01

    The acceleration of high-current beam in Superconducting Radio Frequency (SRF) cavities is a challenging but essential for a variety of advanced accelerators. SRF cavities should be carefully designed to minimize the High Order Modes (HOM) power generated in the cavities by the beam current. The reduction of HOM power we demonstrate in a particular case can be quite large. This paper presents a method to systematically control the HOM resonance frequencies in the initial design phase to minimize the HOM power generation. This method is expected to be beneficial for the design of high SRF cavities addressing a variety of Energy Recovery Linac (ERL) applications.

  13. Operation of a high-gradient superconducting radio-frequency cavity with a non-evaporable getter pump

    International Nuclear Information System (INIS)

    Ciovati, G.; Geng, R.; Lushtak, Y.; Manini, P.; Maccallini, E.; Stutzman, M.

    2017-01-01

    The use of non-evaporable getter (NEG) pumps in particle accelerators has increased significantly over the past few years because of their large pumping speed, particularly for hydrogen, compared to the size of the pump. A concern about using such pumps in superconducting radio-frequency (SRF) accelerators is the possibility of shedding particulates which could then migrate into the SRF cavities and produce field emission, therefore degrading the cavity performance. One option to mitigate such issue is to use sintered getter materials which intrinsically offer superior mechanical and particle retention properties. In this article we present the results from cryogenic RF tests of a high-gradient SRF cavity after being evacuated several times with an NEG pump equipped with sintered getter disks and placed in close proximity to the cavity. The results showed that the cavity performance was not affected by the pump up to the quench gradient of 34 MV/m. As a result of this study, two such NEG pumps have been installed next to a cryomodule in the CEBAF accelerator to maintain ultra-high vacuum in the SRF cryomodule and two adjacent warm girder sections.

  14. Operation of a high-gradient superconducting radio-frequency cavity with a non-evaporable getter pump

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, G., E-mail: gciovati@jlab.org [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Geng, R. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Lushtak, Y.; Manini, P.; Maccallini, E. [SAES Getters, S.p.A, Viale Italia, 77, 20020 Lainate, MI (Italy); Stutzman, M. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States)

    2017-01-11

    The use of non-evaporable getter (NEG) pumps in particle accelerators has increased significantly over the past few years because of their large pumping speed, particularly for hydrogen, compared to the size of the pump. A concern about using such pumps in superconducting radio-frequency (SRF) accelerators is the possibility of shedding particulates which could then migrate into the SRF cavities and produce field emission, therefore degrading the cavity performance. One option to mitigate such issue is to use sintered getter materials which intrinsically offer superior mechanical and particle retention properties. In this article we present the results from cryogenic RF tests of a high-gradient SRF cavity after being evacuated several times with an NEG pump equipped with sintered getter disks and placed in close proximity to the cavity. The results showed that the cavity performance was not affected by the pump up to the quench gradient of 34 MV/m. As a result of this study, two such NEG pumps have been installed next to a cryomodule in the CEBAF accelerator to maintain ultra-high vacuum in the SRF cryomodule and two adjacent warm girder sections.

  15. The quest for high-gradient superconducting cavities

    International Nuclear Information System (INIS)

    Padamsee, H.

    1999-01-01

    Superconducting RF cavities excel in applications requiring continuous waves or long pulse voltages. Since power losses in the walls of the cavity increase as the square of the accelerating voltage, copper cavities become uneconomical as demand for high continuous wave voltage grows with particle energy. For these reasons, RF superconductivity has become an important technology for high energy and high luminosity accelerators. The state of art in performance of sheet metal niobium cavities is best represented by the statistics of more than 300 5-cell, 1.5-GHz cavities built for CEBAF. Key aspects responsible for the outstanding performance of the CEBAF cavities set are the anti-multipactor, elliptical cell shape, good fabrication and welding techniques, high thermal conductivity niobium, and clean surface preparation. On average, field emission starts at the electric field of 8.7 MV/m, but there is a large spread, even though the cavities received nominally the same surface treatment and assembly procedures. In some cavities, field emission was detected as low as 3 MV/m. In others, it was found to be as high as 19 MV/m. As we will discuss, the reason for the large spread in the gradients is the large spread in emitter characteristics and the random occurrence of emitters on the surface. One important phenomenon that limits the achievable RF magnetic field is thermal breakdown of superconductivity, originating at sub-millimeter-size regions of high RF loss, called defects. Simulation reveal that if the defect is a normal conducting region of 200 mm radius, it will break down at 5 MV/m. Producing high gradients and high Q in superconducting cavities demands excellent control of material properties and surface cleanliness. The spread in gradients that arises from the random occurrence of defects and emitters must be reduced. It will be important to improve installation procedures to preserve the excellent gradients now obtained in laboratory test in vertical cryostats

  16. Development of optical inspection system of L-band SRF cavity

    International Nuclear Information System (INIS)

    Tajima, Yujiro; Iwashita, Yoshihisa; Hayano, Hitoshi

    2008-01-01

    The International Linear Collider (ILC) will require about 15,000 1.3 GHz superconducting radio frequency (SRF) accelerating cavities with high accelerating gradient (>35 MV/m) in its main linac. The high yield (80%) of successful high gradient cavities is necessary. Both of the yield and the accelerating gradient of SRF cavities does not reach the required level at present. We think that the gradient of the SRF cavities is limited by irregularities on the interior surface of the cavities, for example, fine dusts (1μm), balls (100μm) and pits (100μm): electrons emitted from the fine dusts by the tunnel effect are accelerated in the electric field, and consume the stored energy of the cavities (Field Emission). The balls and pits cause a breakdown by a magnetic field enhancement or a thermal current concentration (Thermal Breakdown). To prevent these problems the interior surface are treated by polishing and rinsing. The relation between the surface states and the gradient limitations, however, is still not clarified. To study the relation, we are developing an optical inspection system of the interior surface. (author)

  17. New results of development on high efficiency high gradient superconducting rf cavities

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Li, Z. K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hao, Z. K. [Peking Univ., Beijing (China); Liu, K. X. [Peking Univ., Beijing (China); Zhao, H. Y. [OTIC, Ningxia (China); Adolphsen, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-09-01

    We report on the latest results of development on high-efficiency high-gradient superconducting radio frequency (SRF) cavities. Several 1-cell cavities made of large-grain niobium (Nb) were built, processed and tested. Two of these cavities are of the Low Surface Field (LSF) shape. Series of tests were carried out following controlled thermal cycling. Experiments toward zero-field cooling were carried out. The best experimentally achieved results are Eacc = 41 MV/m at Q0 = 6.5×1010 at 1.4 K by a 1-cell 1.3 GHz large-grain Nb TTF shape cavity and Eacc = 49 MV/m at Q0 = 1.5×1010 at 1.8 K by a 1-cell 1.5 GHz large-grain Nb CEBAF upgrade low-loss shape cavity.

  18. JLab SRF Cavity Fabrication Errors, Consequences and Lessons Learned

    International Nuclear Information System (INIS)

    Marhauser, Frank

    2011-01-01

    Today, elliptical superconducting RF (SRF) cavities are preferably made from deep-drawn niobium sheets as pursued at Jefferson Laboratory (JLab). The fabrication of a cavity incorporates various cavity cell machining, trimming and electron beam welding (EBW) steps as well as surface chemistry that add to forming errors creating geometrical deviations of the cavity shape from its design. An analysis of in-house built cavities over the last years revealed significant errors in cavity production. Past fabrication flaws are described and lessons learned applied successfully to the most recent in-house series production of multi-cell cavities.

  19. RF Power Requirements for PEFP SRF Cavity Test

    International Nuclear Information System (INIS)

    Kim, Han Sung; Seol, Kyung Tae; Kwon, Hyeok Jung; Cho, Yong Sub

    2011-01-01

    For the future extension of the PEFP (Proton Engineering Frontier Project) Proton linac, preliminary study on the SRF (superconducting radio-frequency) cavity is going on including a five-cell prototype cavity development to confirm the design and fabrication procedures and to check the RF and mechanical properties of a low-beta elliptical cavity. The main parameters of the cavity are like followings. - Frequency: 700 MHz - Operating mode: TM010 pi mode - Cavity type: Elliptical - Geometrical beta: 0.42 - Number of cells: 5 - Accelerating gradient: 8 MV/m - Epeak/Eacc: 3.71 - Bpeak/Eacc: 7.47 mT/(MV/m) - R/Q: 102.3 ohm - Epeak: 29.68 MV/m (1.21 Kilp.) - Geometrical factor: 121.68 ohm - Cavity wall thickness: 4.3 mm - Stiffening structure: Double ring - Effective length: 0.45 m For the test of the cavity at low temperature of 4.2 K, many subsystems are required such as a cryogenic system, RF system, vacuum system and radiation shielding. RF power required to generate accelerating field inside cavity depends on the RF coupling parameters of the power coupler and quality factor of the SRF cavity and the quality factor itself is affected by several factors such as operating temperature, external magnetic field level and surface condition. Therefore, these factors should be considered to estimate the required RF power for the SRF cavity test

  20. Frequency-tunable SRF cavities for microwave opto-mechanics

    Science.gov (United States)

    Castelli, Alessandro; Martinez, Luis; Pate, Jacob; Thompson, Johnathon; Chiao, Raymond; Sharping, Jay

    Three dimensional SRF (Superconducting Radio Frequency) cavities are known for achieving high quality factors (Q =109 or higher) but suffer from limited frequency tunability once fabricated and cooled to superconducting temperatures. Our end-wall design allows for numerous applications of cavity tuning at temperatures as low as 40 millikelvin. Using a bimorphic piezoelectric transducer, we demonstrate approximately 15 MHz of resonance tunability for the TE011 mode at cryogenic temperatures in a cylindrical reactor grade niobium (Nb) cavity (10% of the range at room temperature). This range doubles when using tunable end-walls on both cavity ends. We report on techniques for improving the Q of multi-component cavities including the use of concave end-walls to reduce fields near the cylinder ends and indium O-rings to reduce resistive losses at the gaps. Three-dimensional SRF cavities of this type have potential applications to quantum information science, precision displacement metrology, and quantum electro-dynamics.

  1. RF control studies for moderate beamtime coupling between SRF cavities

    International Nuclear Information System (INIS)

    Doolittle, L.R.; Wang, D.X.

    1998-01-01

    When an SRF accelerator is designed, there is motivation to move the cavities close together on the beamline. Assuming the beamline apertures are not shrunk as well, this compaction (which will increase the overall accelerating gradient and/or lower the dynamic cryogenic heat load) increases the inter-cavity coupling. Within certain limits, the control system can compensate for this coupling by retuning each of the cavities. This paper describes constraints on the RF system, tuners, couplers, and control systems that are required to provide stable operation of cavities in the presence of inter-cavity coupling that exceeds the loaded bandwidth of an individual cavity

  2. Tunneling study of SRF cavity-grade niobium

    International Nuclear Information System (INIS)

    Proslier, T.; Zasadzinski, J.; Cooley, L.; Pellin, M.; Norem, J.; Elam, J.; Antonine, C. Z.; Rimmer, R.; Kneisel, P.

    2009-01-01

    Niobium, with its very high H C1 , has been used in superconducting radio frequency (SRF) cavities for accelerator systems for 40 years with continual improvement. The quality factor of cavities (Q) is governed by the surface impedance R BCS , which depends on the quasiparticle gap, delta, and the superfluid density. Both of these parameters are seriously affected by surface imperfections (metallic phases, dissolved oxygen, magnetic impurities). Loss mechanism and surface treatments of Nb cavities found to improve the Q factor are still unsolved mysteries. We present here an overview of the capabilities of the point contact tunneling spectroscopy and Atomic layer deposition methods and how they can help understanding the High field Q-drop and the mild baking effect. Tunneling spectroscopy was performed on Nb pieces from the same processed material used to fabricate SRF cavities. Air exposed, electropolished Nb exhibited a surface superconducting gap Delta = 1.55 meV, characteristic of clean, bulk Nb, however the tunneling density of states (DOS) was broadened significantly. Nb pieces treated with the same mild baking used to improve the Q-slope in SRF cavities revealed a much sharper DOS. Good fits to the DOS are obtained using Shiba theory suggesting that magnetic scattering of quasiparticles is the origin of the degraded surface superconductivity and the Q-slope problem of Nb SRF cavities

  3. Magnesium Diboride thin Films, multilayers, and coatings for SRF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Xiaoxing [Temple Univ., Philadelphia, PA (United States)

    2017-08-17

    Superconducting radio frequency (SRF) cavities currently use low-temperature superconductor niobium, and the Nb SRF cavities have approached the performance levels predicted theoretically. Compared to Nb, MgB2 becomes superconducting at a much higher temperature and promises a better RF performance in terms of higher quality factor Q and higher acceleration capability. An MgB2 SRF technology can significantly reduce the operating costs of particle accelerators when these potentials are realized. This project aimed to advance the development of an MgB2 SRF technology. It had two main objectives: (1) materials issues of MgB2 thin films and multilayers related to their applications in SRF cavities; and (2) coating single-cell cavities for testing at RF frequencies. The key technical thrust of the project is the deposition of high quality clean MgB2 films and coatings by the hybrid physical-chemical vapor deposition (HPCVD) technique, which was developed in my group. We have achieved technical progress in each of the two areas. For the first objective, we have confirmed that MgB2 thin film coatings can be used to effectively enhance the vortex penetration field of an SRF cavity. A vortex is a normal region in the shape of spaghetti that threads through a superconductor. Its existence is due to an applied magnetic field that is greater than a so-called lower critical field, Hc1. Once a vortex enters the superconductor, its movement leads to loss. This has been shown to be the reason for an SRF cavity to break down. Thus, enhancing the magnetic field for a vortex to enter the superconductor that forms the SRF cavity has be a goal of intense research. To this end, Gurevich proposed that a coating of thin superconductor layer can impede the vortex entrance. In this project, we have done two important experiment to test this concept. One, we showed that the enhancement of Hc1 can be

  4. Recent Developments in SRF Cavity Science and Performance

    Energy Technology Data Exchange (ETDEWEB)

    G. Ciovati

    2006-08-10

    The performances of SRF cavities made of high purity bulk niobium have been improving in the last few years and surface magnetic fields (Bp) close to the thermodynamic critical field of niobium have been achieved in a few cases. The recommendation made in 2004 in favor of SRF as the technology of choice for the International Linear Collider (ILC), requires improving the reliability of multi-cell cavities operating at accelerating gradients (Eacc) of the order of 35 MV/m. Additionally, a better understanding of the present limitations to cavity performance, such as the high-field Q-drop is needed. This contribution presents some recent developments in SRF cavity science and performance. Among the most significant advances of the last few years, new cavity shapes with lower ratio Bp/Eacc were designed and tested. Cavities made of large-grain niobium became available, promising lower cost at comparable performance to standard fine-grain ones and several tests on single-cell cavities were done to gain a better understanding of high-field losses. In addition, studies to improve the reliability of electropolishing are being carried out by several research groups.

  5. Optimizing Centrifugal Barrel Polishing For Mirror Finish SRF Cavity And RF Tests At Jefferson Lab

    International Nuclear Information System (INIS)

    Palczewski, Ari; Geng, Rongli; Tian, Hui

    2012-01-01

    We performed Centrifugal Barrel Polishing (CBP) on a 1.3 GHz fine grain TESLA single cell cavity and 1.5 GHz fine grain CEBAF high gradient superconducting radio frequency (SRF) single cell cavity following a modified recipe originally developed at Fermi National Accelerator Lab (FNAL). We were able to obtain a mirror like surface similar to that obtained at FNAL, while reducing the number of CBP steps and total processing time. This paper will discuss the change in surface and subsequent cavity performance post CBP, after a 800 C bake (no pre-bake chemistry) and minimal controlled electro-polishing (10 micron). In addition to Q vs. E ACC thermometry mapping with preheating characteristics and optical inspection of the cavity after CBP will also be shown.

  6. Apparatus and method for plasma processing of SRF cavities

    Science.gov (United States)

    Upadhyay, J.; Im, Do; Peshl, J.; Bašović, M.; Popović, S.; Valente-Feliciano, A.-M.; Phillips, L.; Vušković, L.

    2016-05-01

    An apparatus and a method are described for plasma etching of the inner surface of superconducting radio frequency (SRF) cavities. Accelerator SRF cavities are formed into a variable-diameter cylindrical structure made of bulk niobium, for resonant generation of the particle accelerating field. The etch rate non-uniformity due to depletion of the radicals has been overcome by the simultaneous movement of the gas flow inlet and the inner electrode. An effective shape of the inner electrode to reduce the plasma asymmetry for the coaxial cylindrical rf plasma reactor is determined and implemented in the cavity processing method. The processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise way to establish segmented plasma columns. The test structure was a pillbox cavity made of steel of similar dimension to the standard SRF cavity. This was adopted to experimentally verify the plasma surface reaction on cylindrical structures with variable diameter using the segmented plasma generation approach. The pill box cavity is filled with niobium ring- and disk-type samples and the etch rate of these samples was measured.

  7. Design of half-reentrant SRF cavities

    International Nuclear Information System (INIS)

    Meidlinger, M.; Grimm, T.L.; Hartung, W.

    2006-01-01

    The shape of a TeSLA inner cell can be improved to lower the peak surface magnetic field at the expense of a higher peak surface electric field by making the cell reentrant. Such a single-cell cavity was designed and tested at Cornell, setting a world record accelerating gradient [V. Shemelin et al., An optimized shape cavity for TESLA: concept and fabrication, 11th Workshop on RF Superconductivity, Travemuende, Germany, September 8-12, 2003; R. Geng, H. Padamsee, Reentrant cavity and first test result, Pushing the Limits of RF Superconductivity Workshop, Argonne National Laboratory, September 22-24, 2004]. However, the disadvantage to a cavity is that liquids become trapped in the reentrant portion when it is vertically hung during high pressure rinsing. While this was overcome for Cornell's single-cell cavity by flipping it several times between high pressure rinse cycles, this may not be feasible for a multi-cell cavity. One solution to this problem is to make the cavity reentrant on only one side, leaving the opposite wall angle at six degrees for fluid drainage. This idea was first presented in 2004 [T.L. Grimm et al., IEEE Transactions on Applied Superconductivity 15(6) (2005) 2393]. Preliminary designs of two new half-reentrant (HR) inner cells have since been completed, one at a high cell-to-cell coupling of 2.1% (high-k cc HR) and the other at 1.5% (low-k cc HR). The parameters of a HR cavity are comparable to a fully reentrant cavity, with the added benefit that a HR cavity can be easily cleaned with current technology

  8. Performance experience with the CEBAF SRF cavities

    International Nuclear Information System (INIS)

    Reece, C.; Benesch, J.; Drury, M.; Hovater, C.; Mammosser, J.; Preble, J.

    1995-01-01

    The full complement of 169 pairs of niobium superconducting cavities has been installed in the CEBAF accelerator. This paper surveys the performance characteristics of these cavities in vertical tests, commissioning in the tunnel, and operational experience to date. Although installed performance exceeds specifications, and 3.2 GeV beam has been delivered on target, present systems do not consistently preserve the high performance obtained in vertical dewar tests as operational capability. Principal sources of these limitations are discussed

  9. SRF Cavity Surface Topography Characterization Using Replica Techniques

    Energy Technology Data Exchange (ETDEWEB)

    C. Xu, M.J. Kelley, C.E. Reece

    2012-07-01

    To better understand the roll of topography on SRF cavity performance, we seek to obtain detailed topographic information from the curved practical cavity surfaces. Replicas taken from a cavity interior surface provide internal surface molds for fine Atomic Force Microscopy (AFM) and stylus profilometry. In this study, we confirm the replica resolution both on surface local defects such as grain boundary and etching pits and compare the surface uniform roughness with the aid of Power Spectral Density (PSD) where we can statistically obtain roughness parameters at different scales. A series of sampling locations are at the same magnetic field chosen at the same latitude on a single cell cavity to confirm the uniformity. Another series of sampling locations at different magnetic field amplitudes are chosen for this replica on the same cavity for later power loss calculation. We also show that application of the replica followed by rinsing does not adversely affect the cavity performance.

  10. Apparatus and process for passivating an SRF cavity

    Science.gov (United States)

    Myneni, Ganapati Rao; Wallace, John P

    2014-12-02

    An apparatus and process for the production of a niobium cavity exhibiting high quality factors at high gradients is provided. The apparatus comprises a first chamber positioned within a second chamber, an RF generator and vacuum pumping systems. The process comprises placing the niobium cavity in a first chamber of the apparatus; thermally treating the cavity by high temperature in the first chamber while maintaining high vacuum in the first and second chambers; and applying a passivating thin film layer to a surface of the cavity in the presence of a gaseous mixture and an RF field. Further a niobium cavity exhibiting high quality factors at high gradients produced by the method of the invention is provided.

  11. Optimizing SRF Gun Cavity Profiles in a Genetic Algorithm Framework

    International Nuclear Information System (INIS)

    Hofler, Alicia; Evtushenko, Pavel; Marhauser, Frank

    2009-01-01

    Automation of DC photoinjector designs using a genetic algorithm (GA) based optimization is an accepted practice in accelerator physics. Allowing the gun cavity field profile shape to be varied can extend the utility of this optimization methodology to superconducting and normal conducting radio frequency (SRF/RF) gun based injectors. Finding optimal field and cavity geometry configurations can provide guidance for cavity design choices and verify existing designs. We have considered two approaches for varying the electric field profile. The first is to determine the optimal field profile shape that should be used independent of the cavity geometry, and the other is to vary the geometry of the gun cavity structure to produce an optimal field profile. The first method can provide a theoretical optimal and can illuminate where possible gains can be made in field shaping. The second method can produce more realistically achievable designs that can be compared to existing designs. In this paper, we discuss the design and implementation for these two methods for generating field profiles for SRF/RF guns in a GA based injector optimization scheme and provide preliminary results.

  12. Hydroforming SRF Three-cell Cavity from Seamless Niobium Tube

    Energy Technology Data Exchange (ETDEWEB)

    Yamanaka, Masashi [KEK, Tsukuba; Dohmae, Takeshi [KEK, Tsukuba; Hocker, Andy [Fermilab; Inoue, Hitoshi [KEK, Tsukuba; Park, Gunn-Tae [KEK, Tsukuba; Tajima, Tsuyoshi [Los Alamos; Umemori, Kensei [KEK, Tsukuba

    2016-06-01

    We are developing the manufacturing method for superconducting radio frequency (SRF) cavities by using a hydroforming instead of using conventional electron beam welding. We expect higher reliability and reduced cost with hydroforming. For successful hydroforming, high-purity seamless niobium tubes with good formability as well as advancing the hydroforming technique are necessary. Using a seamless niobium tube from ATI Wah Chang, we were able to successfully hydroform a 1.3 GHz three-cell TESLA-like cavity and obtained an Eacc of 32 MV/m. A barrel polishing process was omitted after the hydroforming. The vertical test was carried out with very rough inside surface. We got amazing and interesting result.

  13. High Pressure, High Gradient RF Cavities for Muon Beam Cooling

    CERN Document Server

    Johnson, R P

    2004-01-01

    High intensity, low emittance muon beams are needed for new applications such as muon colliders and neutrino factories based on muon storage rings. Ionization cooling, where muon energy is lost in a low-Z absorber and only the longitudinal component is regenerated using RF cavities, is presently the only known cooling technique that is fast enough to be effective in the short muon lifetime. RF cavities filled with high-pressure hydrogen gas bring two advantages to the ionization technique: the energy absorption and energy regeneration happen simultaneously rather than sequentially, and higher RF gradients and better cavity breakdown behavior are possible than in vacuum due to the Paschen effect. These advantages and some disadvantages and risks will be discussed along with a description of the present and desired RF R&D efforts needed to make accelerators and colliders based on muon beams less futuristic.

  14. Thin Film Approaches to the SRF Cavity Problem: Fabrication and Characterization of Superconducting Thin Films

    Science.gov (United States)

    Beringer, Douglas B.

    Superconducting Radio Frequency (SRF) cavities are responsible for the acceleration of charged particles to relativistic velocities in most modern linear accelerators, such as those employed at high-energy research facilities like Thomas Jefferson National Laboratory's CEBAF and the LHC at CERN. Recognizing SRF as primarily a surface phenomenon enables the possibility of applying thin films to the interior surface of SRF cavities, opening a formidable tool chest of opportunities by combining and designing materials that offer greater benefit. Thus, while improvements in radio frequency cavity design and refinements in cavity processing techniques have improved accelerator performance and efficiency - 1.5 GHz bulk niobium SRF cavities have achieved accelerating gradients in excess of 35 MV/m - there exist fundamental material bounds in bulk superconductors limiting the maximally sustained accelerating field gradient (approximately 45 MV/m for Niobium) where inevitable thermodynamic breakdown occurs. With state of the art niobium based cavity design fast approaching these theoretical limits, novel material innovations must be sought in order to realize next generation SRF cavities. One proposed method to improve SRF performance is to utilize thin film superconducting-insulating-superconducting (SIS) multilayer structures to effectively magnetically screen a bulk superconducting layer such that it can operate at higher field gradients before suffering critically detrimental SRF losses. This dissertation focuses on the production and characterization of thin film superconductors for such SIS layers for radio-frequency applications.

  15. Design features of a seven-cell high-gradient superconducting cavity

    International Nuclear Information System (INIS)

    Liska, D.J.; Ledford, J.; Black, S.; Spalek, G.; DiMarco, J.N.

    1992-01-01

    A cavity development program is in place at Los Alamos National Laboratory to evaluate structures that could be used to accelerate pions. The work is being guided by the conceptual design of PILAC, a high-gradient superconducting linac for raising the energy of rapidly decaying intense pion beams generated by Los Alamos Meson Physics Facility (LAMPF) to 1 GeV. The specification requires a cavity gradient of 12.5 MV/m at 805 MHz. The design of a seven-cell prototype cavity to achieve these high gradients has been completed by the Accelerator Technology division. The cavity is presently under procurement for high power testing a 2.0 K in 1993

  16. Geometric optimization of the 56 MHz SRF cavity and its frequency table

    International Nuclear Information System (INIS)

    Chang, X.; Ben-Zvi, I.

    2008-01-01

    It is essential to know the frequency of a Superconducting Radio Frequency (SRF) cavity at its 'just being fabricated' stage because frequency is the key parameter in constructing the cavity. In this paper, we report our work on assessing it. We can estimate the frequency change from stage to stage theoretically and/or by simulation. At the operating stage, the frequency can be calculated accurately, and, from this value, we obtain the frequencies at other stages. They are listed in a table that serves to check the processes from stage to stage. Equally important is optimizing the geometric shape of the SRF cavity so that the peak electric-field and peak magnetic-field are as low as possible. It is particularly desirable in the 56MHz SRF cavity of RHIC to maximize the frequency sensitivity of the slow tuner. After undertaking such optimization, our resultant peak electric-field is only 44.1MV/m, and the peak magnetic-field is 1049G at 2.5MV of voltage across the cavity gap. To quench superconductivity in an SRF cavity, it is reported that the limit of the peak magnetic-field is 1800G (1), and that of the peak electric-field is more than l00MV/m for a SRF cavity (2). Our simulations employed the codes Superfish and Microwave Studio

  17. Status and first measurement results for a high gradient CH-cavity

    Energy Technology Data Exchange (ETDEWEB)

    Almomani, Ali; Ratzinger, Ulrich [Institut fuer Angewandte Physik, Frankfurt Universitaet, Frankfurt am Main (Germany)

    2016-07-01

    This pulsed linac activity aims on compact designs and on a considerable increase of the voltage gain per meter. A high gradient CH {sup *} cavity operated at 325 MHz was developed at IAP {sup *} Frankfurt. The mean effective accelerating field for this cavity is expected well above 10 MV/m at β=0.164. This cavity is developed within a funded project. The results might influence the rebuilt of the UNILAC {sup *} Alvarez section, aiming to achieve the beam intensities specified for the GSI {sup *} FAIR project (15 mA U28+). Another motivation is the development of an efficient pulsed ion accelerator for significantly higher energies like 60 AMeV. The new GSI 3 MW Thales klystron test stand will be used for the cavity RF power tests. Detailed studies on two different types of copper plating will be performed with this cavity.

  18. Industrialization of the nitrogen-doping preparation for SRF cavities for LCLS-II

    Science.gov (United States)

    Gonnella, D.; Aderhold, S.; Burrill, A.; Daly, E.; Davis, K.; Grassellino, A.; Grimm, C.; Khabiboulline, T.; Marhauser, F.; Melnychuk, O.; Palczewski, A.; Posen, S.; Ross, M.; Sergatskov, D.; Sukhanov, A.; Trenikhina, Y.; Wilson, K. M.

    2018-03-01

    The Linac Coherent Light Source II (LCLS-II) is a new state-of-the-art coherent X-ray source being constructed at SLAC National Accelerator Laboratory. It employs 280 superconducting radio frequency (SRF) cavities in order operate in continuous wave (CW) mode. To reduce the overall cryogenic cost of such a large accelerator, nitrogen-doping of the SRF cavities is being used. Nitrogen-doping has consistently been shown to increase the efficiency of SRF cavities operating in the 2.0 K regime and at medium fields (15-20 MV/m) in vertical cavity tests and horizontal cryomodule tests. While nitrogen-doping's efficacy for improvement of cavity performance was demonstrated at three independent labs, Fermilab, Jefferson Lab, and Cornell University, transfer of the technology to industry for LCLS-II production was not without challenges. Here we present results from the beginning of LCLS-II cavity production. We discuss qualification of the cavity vendors and the first cavities from each vendor. Finally, we demonstrate that nitrogen-doping has been successfully transferred to SRF cavity vendors, resulting in consistent production of cavities with better cryogenic efficiency than has ever been achieved for a large-scale accelerator.

  19. Thin Film Approaches to the SRF Cavity Problem Fabrication and Characterization of Superconducting Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Beringer, Douglas [College of William and Mary, Williamsburg, VA (United States)

    2017-08-01

    Superconducting Radio Frequency (SRF) cavities are responsible for the acceleration of charged particles to relativistic velocities in most modern linear accelerators, such as those employed at high-energy research facilities like Thomas Jefferson National Laboratory’s CEBAF and the LHC at CERN. Recognizing SRF as primarily a surface phenomenon enables the possibility of applying thin films to the interior surface of SRF cavities, opening a formidable tool chest of opportunities by combining and designing materials that offer greater performance benefit. Thus, while improvements in radio frequency cavity design and refinements in cavity processing techniques have improved accelerator performance and efficiency – 1.5 GHz bulk niobium SRF cavities have achieved accelerating gradients in excess of 35 MV/m – there exist fundamental material bounds in bulk superconductors limiting the maximally sustained accelerating field gradient (≈ 45 MV/m for Nb) where inevitable thermodynamic breakdown occurs. With state of the art Nb based cavity design fast approaching these theoretical limits, novel material innovations must be sought in order to realize next generation SRF cavities. One proposed method to improve SRF performance is to utilize thin film superconducting-insulating-superconducting (SIS) multilayer structures to effectively magnetically screen a bulk superconducting layer such that it can operate at higher field gradients before suffering critically detrimental SRF losses. This dissertation focuses on the production and characterization of thin film superconductors for such SIS layers for radio frequency applications. Correlated studies on structure, surface morphology and superconducting properties of epitaxial Nb and MgB2 thin films are presented.

  20. Activities on cryostats and SRF cavities at the I.P.N. Orsay laboratory

    International Nuclear Information System (INIS)

    Buelher, S.; Caruette, A.; Fouaidy, M.; Junquera, T.

    1993-01-01

    The main effort of the SRF community at Orsay during the last five years was concentrated on the MACSE project (study, construction, assembly and test of 3 cryostats), participation to the TESLA project and R and D activities in close collaboration with the Saclay SRF group. 3 major topics are outlined and briefly discussed: cryogenics, scanning surface thermometers for diagnostics on SRF cavities and thermal behaviour analysis of HOM couplers. The main results obtained in this frame since the 5th SC workshop at Hamburg in 1991 are presented. (authors) 12 refs., 17 figs., 6 tabs

  1. SRF for neutrino factories

    International Nuclear Information System (INIS)

    Padamsee, H.

    2003-01-01

    The Neutrino Factory calls for nearly 500 meters of 200 MHz SRF cavities to provide 7.5 GV. Such a facility is more demanding than the largest SRF installation to date, i.e., LEP-II, where 500 m of niobium-coated copper cavities provided more than 3 GV of acceleration. Based on the high real estate gradient desired to minimize muon loss, superconducting cavities are selected to provide active gradients of 15 - 17 MV/m, and a real estate gradient of 7.5 MV/m. At such high gradients, the peak RF power demand for copper cavities would become prohibitively expensive. By virtue of low losses, SC cavities can be filled slowly (rise time 3 ms) reducing the peak power demand to roughly half MW per cell. (author)

  2. WAVEGUIDE COUPLER KICK TO BEAM BUNCH AND CURRENT DEPENDENCY ON SRF CAVITIES

    International Nuclear Information System (INIS)

    Genfa Wu; Haipeng Wang; Charles Reece; Robert Rimmer

    2008-01-01

    JLAB SRF cavities employ waveguide type fundamental power couplers (FPC). The FPC design for the 7-cell upgrade cavities was optimized to minimize the dipole field kick. For continuous wave (CW) operation, the forwarding RF power will be at different magnitude to drive the different beam current and cavity gradient. This introduces some deviation from optimized FPC field for varying beam loading. This article analyzes the beam behavior both in centroid kick and head-tail kick under different beam loading conditions

  3. Root Causes of Field Emitters in SRF Cavities Placed in CEBAF Tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli

    2016-05-01

    It has been suspected that appearance of new field emitters can occur in SRF cavities after their placement in accelerator tunnel for long term beam operation. This apparently has been the case for CEBAF. However, no physical evidence has been shown in the past. In this contribution, we will report on the recent results concerning the root cause of field emitters in SRF cavities placed in CEBAF tunnel. We will discuss these results in the context of high-reliability and low-cryogenic-loss operation of CEBAF.

  4. Observation of Stable Low Surface Resistance in Large-Grain Niobium SRF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Huang, Shichun [Institute of Modern Physics (IMP)/Chinese Academy of Sciences (CAS), Lanzhou (China)

    2016-05-01

    Low surface resistance, or high unloaded quality factor (Q0), superconducting radio frequency (SRF) cavities are being pursued actively nowadays as their application in large-scale CW SRF accelerators can save capital and operational cost in cryogenics. There are different options in realization of such cavities. One of them is the large-grain (LG) niobium cavity. In this contribution, we present new experimental results in evaluation of LG niobium cavities cooled down in the presence of an external magnetic field. High Q0 values are achieved even with an ambient magnetic field of up to 100 mG. More over, it is observed that these high Q0 values are super-robust against repeated quench, literally not affected at all after the cavity being deliberately quenched for hundreds of times in the presence of an ambient magnetic field of up to 200 mG.

  5. Analysis of mechanical fabrication experience with CEBAF's production SRF cavities

    International Nuclear Information System (INIS)

    Mammosser, J.; Kneisel, P.; Benesch, J.

    1993-06-01

    CEBAF has received a total of 360 five-cell niobium cavities, the largest group of industrially fabricated superconducting cavities so far. An extensive data base exists on the fabrication, surface treatment, assembly and cavity performance parameters. Analysis of the mechanical features of the cavities includes the following: the spread in fabrication tolerances of the cells derived from field profiles of the ''as fabricated'' cavities and the ''as fabricated'' external Q-values of the fundamental power coupler compared to dimensional deviations. A comparison is made of the pressure sensitivity of cavities made of materials from different manufacturers between 760 torr (4.2 K) and 23 torr (2 K)

  6. Thermal behaviour analysis of SRF cavities and superconducting HOM couplers

    International Nuclear Information System (INIS)

    Fouaidy, M.; Junquera, T.

    1993-01-01

    Two individual papers appear in this report, titled Thermal model calculations in superconducting RF cavities, and Thermal study of HOM couplers for superconducting RF cavities. Both were indexed separately for the INIS database. (R.P.)

  7. Optimization of Pulsed Operation of the Superconducting Radio-Frequency (SRF) Cavities at the Spallation Neutron Source (SNS)

    International Nuclear Information System (INIS)

    Kim, Sang-Ho; Campisi, Isidoro E.

    2007-01-01

    In order to address the optimization in a pulsed operation, a systematic computational analysis has been made in comparison with operational experiences in superconducting radio-frequency (SRF) cavities at the Spallation Neutron Source (SNS). From the analysis it appears that the SNS SRF cavities can be operated at temperatures higher than 2.1 K, a fact resulting from both the pulsed nature of the superconducting cavities, the specific configuration of the existing cryogenic plant and the operating frequency

  8. Flange joint system for SRF cavities utilizing high force spring clamps for low particle generation

    Science.gov (United States)

    None

    2017-09-05

    A flange joint system for SRF cavities. The flange joint system includes a set of high force spring clamps that produce high force on the simple flanges of Superconducting Radio Frequency (SRF) cavities to squeeze conventional metallic seals. The system establishes the required vacuum and RF-tight seal with minimum particle contamination to the inside of the cavity assembly. The spring clamps are designed to stay within their elastic range while being forced open enough to mount over the flange pair. Upon release, the clamps have enough force to plastically deform metallic seal surfaces and continue to a new equilibrium sprung dimension where the flanges remain held against one another with enough preload such that normal handling will not break the seal.

  9. Evaluation Of Silicon Diodes As IN-SITU Cryogenic Field Emission Detectors For SRF Cavity Development

    International Nuclear Information System (INIS)

    Palczewski, Ari; Geng, Rongli

    2012-01-01

    We performed in-situ cryogenic testing of four silicon diodes as possible candidates for field emission (FE) monitors of superconducting radio frequency (SRF) cavities during qualification testing and in accelerator cryo-modules. We evaluated diodes from 2 companies - from Hamamatsu corporation model S1223-01; and from OSI Optoelectronics models OSD35-LR-A, XUV-50C, and FIL-UV20. The measurements were done by placing the diodes in superfluid liquid helium near the top of a field emitting 9-cell cavity during its vertical test. For each diode, we will discuss their viability as a 2K cryogenic detector for FE mapping of SRF cavities and the directionality of S1223-01 in such environments. We will also present calibration curves between the diodes and JLab's standard radiation detector placed above the Dewar's top plate.

  10. SRF Cavity and Materials R&D at Fermilab

    CERN Document Server

    Khabiboulline, N; Bellantoni, L; Berenc, T; Boffo, C; Carcagno, R; Chapman, C; Edwards, H; Elementi, L; Foley, M; Hahn, E; Hicks, D; Mitchell, D; Rowe, A; Solyak, N; Terechkine, Yu

    2004-01-01

    Two 3.9 GHz superconducting RF cavities are under development at FNAL for use in the upgraded Photoinjector Facility. A TM110 mode cavity will provide streak capability for bunch slice diagnostics, and a TM010 mode cavity will provide linearization of the accelerating gradient before compression for better emittance. The status of these two efforts and a review of the FNAL infrastructure development will be given.

  11. Dealing with a large installation of SRF cavities: Characterizing limitations and exploiting operational flexibility

    International Nuclear Information System (INIS)

    C. Reece; B. Madre; L. Doolittle; J. Delayen

    1999-01-01

    Linacs using a large number of SRF cavities can have an awkwardly large number of degrees of freedom for operational setup. The cost and robustness of operation as a function of operating gradient is a particular characteristic of each cavity system and the intended beamloading. A systematic characterization of these limitations has been developed which yields a valuable guide for development resource allocation. In addition, a software tool has been developed which enables the CEBAF machine operator to conveniently exploit the flexibility that results from the many degrees of freedom in response to changing programmatic needs. The two CEBAF SRF linacs each have about 160 independently-controlled SRF cavities. The software utility (LEM++) establishes the operationally optimum gradient in each cavity in response to the operator providing only three of the following four parameters: linac voltage, anticipated beam current, rf cryoheat load, and net rf trip rate. The utility is now fully operational at CEBAF. The methods employed and particular features useful for operations will be presented. The interactive process that has brought the software to its current form will also be discussed. The analysis scheme used to characterize the limitations of the ensemble of cavities will be presented as well

  12. High gradient RF test results of S-band and C-band cavities for medical linear accelerators

    Science.gov (United States)

    Degiovanni, A.; Bonomi, R.; Garlasché, M.; Verdú-Andrés, S.; Wegner, R.; Amaldi, U.

    2018-05-01

    TERA Foundation has proposed and designed hadrontherapy facilities based on novel linacs, i.e. high gradient linacs which accelerate either protons or light ions. The overall length of the linac, and therefore its cost, is almost inversely proportional to the average accelerating gradient. With the scope of studying the limiting factors for high gradient operation and to optimize the linac design, TERA, in collaboration with the CLIC Structure Development Group, has conducted a series of high gradient experiments. The main goals were to study the high gradient behavior and to evaluate the maximum gradient reached in 3 and 5.7 GHz structures to direct the design of medical accelerators based on high gradient linacs. This paper summarizes the results of the high power tests of 3.0 and 5.7 GHz single-cell cavities.

  13. Performance of 3.9 GHz SRF cavities at Fermilab's ILCTA_MDB nhorizontal test stand

    Energy Technology Data Exchange (ETDEWEB)

    Harms, Elvin; Hocker, Andy; /Fermilab

    2008-08-01

    Fermilab is building a cryomodule containing four 3.9 GHz superconducting radio frequency (SRF) cavities for the Free electron LASer in Hamburg (FLASH) facility at the Deutsches Elektronen-SYnchrotron (DESY) laboratory. Before assembling the cavities into the cryomodule, each individual cavity is tested at Fermilab's Horizontal Test Stand (HTS). The HTS provides the capability to test fully-dressed SRF cavities at 1.8 K with high-power pulsed RF in order to verify that the cavities achieve performance requirements under these conditions. The performance at the HTS of the 3.9 GHz cavities built for FLASH is presented here.

  14. Buffer Chemical Polishing and RF Testing of the 56 MHz SRF Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Burrill,A.

    2009-01-01

    The 56 MHz cavity presents a unique challenge in preparing it for RF testing prior to construction of the cryomodule. This challenge arises due to the physical dimensions and subsequent weight of the cavity, and is further complicated by the coaxial geometry, and the need to properly chemically etch and high pressure rinse the entire inner surface prior to RF testing. To the best of my knowledge, this is the largest all niobium SRF cavity to be chemically etched and subsequently tested in a vertical dewar at 4K, and these processes will be the topic of this technical note.

  15. SRF cavity testing using a FPGA Self Excited Loop

    CERN Document Server

    Ben-Zvi, Ilan

    2018-01-01

    This document provides a detailed description of procedures for very-high precision calibration and testing of superconducting RF cavities using digital Low-Level RF (LLRF) electronics based on Field Programmable Gate Arrays (FPGA). The use of a Self-Excited Loop with an innovative procedure for fast turn-on allows the measurement of the forward, reflected and transmitted power from a single port of the directional coupler in front of the cavity, thus eliminating certain measurement errors. Various procedures for measuring the quality factor as a function of cavity fields are described, including a single RF pulse technique. Errors are estimated for the measurements.

  16. Modeling the interaction of a heavily beam loaded SRF cavity with its low-level RF feedback loops

    Science.gov (United States)

    Liu, Zong-Kai; Wang, Chaoen; Chang, Lung-Hai; Yeh, Meng-Shu; Chang, Fu-Yu; Chang, Mei-Hsia; Chang, Shian-Wen; Chen, Ling-Jhen; Chung, Fu-Tsai; Lin, Ming-Chyuan; Lo, Chih-Hung; Yu, Tsung-Chi

    2018-06-01

    A superconducting radio frequency (SRF) cavity provides superior stability to power high intensity light sources and can suppress coupled-bunch instabilities due to its smaller impedance for higher order modes. Because of these features, SRF cavities are commonly used for modern light sources, such as the TLS, CLS, DLS, SSRF, PLS-II, TPS, and NSLS-II, with an aggressive approach to operate the light sources at high beam currents. However, operating a SRF cavity at high beam currents may result with unacceptable stability problems of the low level RF (LLRF) system, due to drifts of the cavity resonant frequency caused by unexpected perturbations from the environment. As the feedback loop gets out of control, the cavity voltage may start to oscillate with a current-dependent characteristic frequency. Such situations can cause beam abort due to the activation of the interlock protection system, i.e. false alarm of quench detection. This malfunction of the light source reduces the reliability of SRF operation. Understanding this unstable mechanism to prevent its appearance becomes a primary task in the pursuit of highly reliable SRF operation. In this paper, a Pedersen model, including the response of the LLRF system, was used to simulate the beam-cavity interaction of a SRF cavity under heavy beam loading. Causes for the onset of instability at high beam current will be discussed as well as remedies to assure the design of a stable LLRF system.

  17. Progress in the Development of SRF Cavity Tuners Based on Magnetic Smart Materials

    International Nuclear Information System (INIS)

    C. Joshi; A. Pappo; D. Upham; J. Preble

    2001-01-01

    Energen, Inc. has developed and demonstrated an SRF cavity tuning mechanism based on magnetic smart materials. Magnetic ''smart'' materials change their shape in a reversible and repeatable manner when exposed to a small magnetic field. A fine-tuning mechanism with a 2 kHz tuning range on a nominal resonant frequency of 1.497 GHz. was successfully demonstrated in 1999 [1]. Since then, Energen has been developing a tuning mechanism based on its linear stepper motors. These stepper motors are designed to deliver high-force precision linear motion of tens of millimeters at cryogenic temperatures. A locking mechanism built into the stepper motor enables the tuner to be locked into position when the power is turned off. This new tuning technology will eliminate the mechanical feeds through the vacuum jacket and reduce the complexity of the cryostat design and assembly. Performance and capabilities of a prototype SRF cavity tuner will be reported

  18. SRF cavity testing using a FPGA Self Excited Loop

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Zvi, I. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-08-30

    Various authors have previously studied the theory and practice of cavity testing, notably an extensive treatment by Powers [1] and Padamsee [2]. The advent of the digital Low Level RF (LLRF) electronics based on Field Programmable Logic Arrays (FPGA) provides various improvements over the rather complex systems used in the past as well as enabling new measurement techniques.In this document we reintroduce a technique that seems to have fallen out of practice in recent times, that is obtaining the coupling constant β through measurements from just one port, the reflected power port, of the directional coupler placed in front of the cavity.

  19. Quench dynamics in SRF cavities: can we locate the quench origin with 2nd sound?

    International Nuclear Information System (INIS)

    Maximenko, Yulia; Segatskov, Dmitri A.

    2011-01-01

    A newly developed method of locating quenches in SRF cavities by detecting second-sound waves has been gaining popularity in SRF laboratories. The technique is based on measurements of time delays between the quench as determined by the RF system and arrival of the second-sound wave to the multiple detectors placed around the cavity in superfluid helium. Unlike multi-channel temperature mapping, this approach requires only a few sensors and simple readout electronics; it can be used with SRF cavities of almost arbitrary shape. One of its drawbacks is that being an indirect method it requires one to solve an inverse problem to find the location of a quench. We tried to solve this inverse problem by using a parametric forward model. By analyzing the data we found that the approximation where the second-sound emitter is a near-singular source does not describe the physical system well enough. A time-dependent analysis of the quench process can help us to put forward a more adequate model. We present here our current algorithm to solve the inverse problem and discuss the experimental results.

  20. Effect of cathode shape on vertical buffered electropolishing for niobium SRF cavities

    Science.gov (United States)

    Jin, S.; Wu, A. T.; Lu, X. Y.; Rimmer, R. A.; Lin, L.; Zhao, K.; Mammosser, J.; Gao, J.

    2013-09-01

    This paper reports the research results of the effect of cathode shape during vertical buffered electropolishing (BEP) by employing a demountable single cell niobium (Nb) superconducting radio frequency (SRF) cavity. Several different cathode shapes such as, for instance, bar, ball, ellipsoid, and wheels of different diameters have been tested. Detailed electropolishing parameters including I-V characteristic, removal rate, surface roughness, and polishing uniformity at different locations inside the demountable cavity are measured. Similar studies are also done on conventional electropolishing (EP) for comparison. It is revealed that cathode shape has dominant effects for BEP especially on the obtaining of a suitable polishing condition and a uniform polishing rate in an Nb SRF single cell cavity. EP appears to have the same tendency. This paper demonstrates that a more homogeneous polishing result can be obtained by optimizing the electric field distribution inside the cavity through the modification of the cathode shape given the conditions that temperature and electrolyte flow are kept constant. Electric field distribution and electrolyte flow patterns inside the cavity are simulated via Poisson-Superfish and Solidworks respectively. With the optimal cathode shape, BEP shows a much faster polishing rate of ∼2.5 μm/min and is able to produce a smoother surface finish in the treatments of single cell cavities in comparison with EP.

  1. Effect of cathode shape on vertical buffered electropolishing for niobium SRF cavities

    International Nuclear Information System (INIS)

    Jin, S.; Wu, A.T.; Lu, X.Y.; Rimmer, R.A.; Lin, L.; Zhao, K.; Mammosser, J.; Gao, J.

    2013-01-01

    This paper reports the research results of the effect of cathode shape during vertical buffered electropolishing (BEP) by employing a demountable single cell niobium (Nb) superconducting radio frequency (SRF) cavity. Several different cathode shapes such as, for instance, bar, ball, ellipsoid, and wheels of different diameters have been tested. Detailed electropolishing parameters including I–V characteristic, removal rate, surface roughness, and polishing uniformity at different locations inside the demountable cavity are measured. Similar studies are also done on conventional electropolishing (EP) for comparison. It is revealed that cathode shape has dominant effects for BEP especially on the obtaining of a suitable polishing condition and a uniform polishing rate in an Nb SRF single cell cavity. EP appears to have the same tendency. This paper demonstrates that a more homogeneous polishing result can be obtained by optimizing the electric field distribution inside the cavity through the modification of the cathode shape given the conditions that temperature and electrolyte flow are kept constant. Electric field distribution and electrolyte flow patterns inside the cavity are simulated via Poisson–Superfish and Solidworks respectively. With the optimal cathode shape, BEP shows a much faster polishing rate of ∼2.5 μm/min and is able to produce a smoother surface finish in the treatments of single cell cavities in comparison with EP.

  2. Studies of HOMs in chains of SRF cavities using state-space concatenation scheme

    Energy Technology Data Exchange (ETDEWEB)

    Galek, Tomasz; Heller, Johann; Flisgen, Thomas; Brackebusch, Korinna; Rienen, Ursula van [Institut fuer Allgemeine Elektrotechnik, Universitaet Rostock (Germany)

    2016-07-01

    The design of modern superconducting radio frequency cavities for acceleration of charged particle bunches requires intensive numerical simulations, as they typically arise as modules of several multi-cell cavities. A wide variety of parameters vital to the proper operation of accelerating cavities must be optimized and studied. One of the most important issues concerning the SRF cavities is the influence of the higher order modes on the beam quality, in this contribution. For TESLA-like structures with 1.3 GHz accelerating mode, higher order modes are calculated up to 4 GHz, the external quality factor and the shunt/geometrical impedance spectra are analyzed. To compute properties of complete RF modules the state-space concatenation scheme is used. The aspects of the concatenation scheme and its application to the bERLinPro's chain of cavities is discussed.

  3. Deep drawing experiences of niobium disk for PEFP SRF cavity prototype

    International Nuclear Information System (INIS)

    Kim, Han Sung; An, Sun; Zhang, Liping; Tang, Yazhe; Li, Ying Min; Kwon, Hyeok Jung; Cho, Yong Sub

    2009-01-01

    A superconducting radio frequency (SRF) cavity with a geometrical beta of 0.42 has been designed to accelerate a proton beam after 100 MeV for an extension of Proton Engineering Frontier Project (PEFP). The designed cavity shape is an elliptical and the resonant frequency is 700 MHz. In order to confirm the RF and mechanical properties of the cavity, two prototypes of copper cavities have been fabricated and tested. Based on the experiences gained with the copper prototypes, two niobium prototypes have been designed. One is two-cell cavity and the other is five cell cavity. The two-cell cavity is for finalizing the niobium cavity production procedure and testing the cavity RF properties at a low temperature and moderate power level. The five-cell cavity is for checking the production quality and testing vertical test system in the future. Both of them are under fabrication. Through the fabrication of the niobium prototype, several issues such as deep drawing, electron beam welding and surface treatment will be addressed. The drawing of the PEPF SRF low beta cavity is shown in Fig. 1. Major parameters for the cavity are like following. - Frequency: 700 MHz - Operating mode: TM010 pi mode - Cavity type: Elliptical - Geometrical beta: 0.42 - Number of cells: 5 per cavity - Accelerating gradient: 8 MV/m - Epeak/Eacc: 3.71 - Bpeak/Eacc: 7.47 mT/(MV/m) - R/Q: 102.3 ohm - Epeak: 29.68 MV/m - Field flatness: 1.56 % - Cell to cell coupling: 1.41 % - Geometrical factor: 121.68 ohm - Cavity wall thickness: 4.3 mm - Lorentz force detuning: 0.4 Hz/(MV/m)2 - Stiffening structure: Double ring - Effective length: 0.45 m - External Q of FPC: 8.0E5 ±20 % - HOM load: less than 2 W - HOM Qext requirement: less than 3.0E5 At present, all the niobium disk and plates for cavity and NbTi flanges for beam pipe flange are prepared

  4. A Family of L-band SRF Cavities for High Power Proton Driver Applications

    International Nuclear Information System (INIS)

    Rimmer, Robert; Marhauser, Frank

    2009-01-01

    Recent global interest in high duty factor or CW superconducting linacs with high average beam power highlights the need for robust and reliable SRF structures capable of delivering high average RF power to the beam with moderate HOM damping, low interception of halo and good efficiency. Potential applications include proton or H- drivers for spallation neutron sources, neutrino physics, waste transmutation, subcritical reactors, and high-intensity high-energy physics experiments. We describe a family of SRF cavities with a range of Betas capable of transporting beam currents in excess of 10 mA CW with large irises for minimal interception of halo and HOM and power couplers capable of supporting high average power operation. Goals include an efficient cell shape, high packing factor for efficient real-estate gradient and strong HOM damping to ensure stable beam operation,

  5. Development efforts on helium vessel for 5 cell - 650 MHz SRF cavity at RRCAT

    International Nuclear Information System (INIS)

    Kumar, Abhay; Kumar, Pankaj; Sandha, R.S.; Dutta, Subhajit; Soni, Rakesh; Dwivedi, Jishnu; Thakurta, A.C.; Bhatnagar, V.K.; Mundra, G.

    2011-01-01

    The work focuses on the development of helium vessel which houses a 5 cell - 650 MHz SRF niobium cavity and serves as a helium bath to maintain the cavity at 2 K. The vessel has provision for changing the axial length of the cavity for tuning purpose by using a tuning mechanism and a large bellow. Titanium has been chosen as a material of construction of the vessel due to its coefficient of thermal expansion being close to that of niobium. Efforts have been initiated to understand the functional requirements, design requirements, acceptance criteria for design and analysis, non-destructive examination requirements, inspection and testing requirements, manufacturing technology of the titanium vessel and its integration with the SRF cavity. The welding assumes a special significance as titanium is highly reactive and ductility of the weld joint is lost in the presence of air and other impurities. A trial vessel has been conceptualised having typical sizes and geometries. The manufacturing features of vessel are based on ASME B and PV Code, Section VIII Division-1 and manufacturing of this vessel has been started at an Indian industry. Quality assurance plan for this work is developed. The paper describes the work done at RRCAT on the functional and integration requirements, overall design requirements, design methodology to achieve code conformance, manufacturing technology and QAP being used in the development of helium vessel. (author)

  6. SQUID-based Nondestructive Testing Instrument of Dished Niobium Sheets for SRF Cavities

    International Nuclear Information System (INIS)

    Q. S. Shu; I. Ben-Zvi; G. Cheng; I. M. Phipps; J. T. Susta; P. Kneisel; G. Myneni; J. Mast; R. Selim

    2007-01-01

    Currently available technology can only inspect flat sheets and allow the elimination of defective flat sheets before the expensive forming and machining of the SRF cavity half-cells, but it does not eliminate the problem of remaining or uncovered surface impurities after partial chemical etching of the half-cells, nor does it detect any defects that may have been added during the fabrication of the half-cells. AMAC has developed a SQUID scanning system based on eddy current technique that allows the scanning of curved Nb samples that are welded to make superconducting RF cavity half-cells. AMAC SQUID scanning system successfully located the defects (Ta macro particles about 100 mm diameter) in a flat Nb sample (top side) and was able to also locate the defects in a cylindrical surface sample (top side). It is more significant that the system successfully located the defects on the backside of the flat sample and curved sample or 3-mm from the top surface. The 3-D SQUID-based Nondestructive instrument will be further optimized and improved in making SRF cavities and allow inspection and detection during cavity manufacturing for achieving highest accelerating fields

  7. RECENT DEVELOPMENTS IN SRF CAVITY SCIENCE AND PERFORMANCE

    International Nuclear Information System (INIS)

    Gianluigi Ciovati

    2006-01-01

    A recipe based on centrifugal barrel polishing (CBP) and electropolishing (EP), applied on newly designed single-cells, led to the achievement of B p values close to the thermodynamic critical field of Nb and to new records in terms of accelerating gradients The fabrication of cavities made of large-grain Nb is emerging as a viable option to reduce the material cost without sacrificing the performance. The Q-drop is not caused exclusively by losses at grain boundaries in Nb. Baking is the only known remedy against the Q-drop and its effect seems to be related to a change of the properties of the Nb up to a depth of about 20 nm. 120 C is the optimum temperature and the baking time can be reduced to 12 h. Cleaning techniques such as high-pressure rinse (HPR) are being studied in detail in order to be optimized for mass-production. Dry-ice cleaning may become a complementary cleaning method. Work is being done to better understand and to improve the EP process

  8. A SRF niobium cylindrical cavity with a large silicon nitride niobium-coated membrane as one end-wall

    Science.gov (United States)

    Martinez, Luis; Castelli, Alessandro; Pate, Jacob; Thompson, Johnathon; Delmas, William; Sharping, Jay; Chiao, Raymond; Chiao Team; Sharping Team

    The development of large silicon nitride membranes and niobium film deposition techniques motivate new architectures in opto-mechanics and microwave devices that can exploit the extremely high Q's obtainable with superconducting radio frequency (SRF) niobium cavities. We present a X-band SRF cylindrical cavity-membrane system in which one end-wall of the cavity is replaced by a niobium coated centimeter-sized silicon nitride membrane. We report moderately high Q factors above 10 million. Experimental results characterizing the system and potential future applications for such schemes in microwave devices and optomechanics are discussed.

  9. Design, Fabrication and Testing of Medium-Beta 650 MHz SRF Cavity Prototypes for Project-X

    International Nuclear Information System (INIS)

    Marhauser, F.; Clemens, W.A.; Henry, J.; Kneisel, P.; Martin, R.; Rimmer, R.A.; Slack, G.; Turlington, L.; Williams, R.S.

    2011-01-01

    A new type of superconducting radio frequency (SRF) cavity shape with a shallow equator dome to reduce electron impact energies for suppressing multipacting barriers has been proposed. The shape is in consideration for the first time in the framework of Project-X to design a potential multi-cell cavity candidate for the medium-beta section of the SRF proton CW linac operating at 650 MHz. Rationales covering the design of the multi-cell cavity, the manufacture, post-processing and high power testing of two single-cell prototypes are presented.

  10. Fundamental damper power calculation of the 56 MHz SRF cavity for RHIC

    International Nuclear Information System (INIS)

    Wu, Q.; Bellavia, S.; Ben-Zvi, I.; Grau, M.; Miglionico, G.; Pai, C.

    2011-01-01

    At each injection period during RHIC's operation, the beam's frequency sweeps across a wide range, and some of its harmonics will cross the frequency of the 56MHz SRF cavity. To avoid excitation of the cavity at these times, we designed a fundamental damper for the quarter-wave resonator to damp the cavity heavily. The power extracted by the fundamental damper should correspond to the power handling ability of the system at all stages. In this paper, we discuss the power output from the fundamental damper when it is fully extracted, inserted, and any intermediate point. A Fundamental Damper (FD) will greatly reduce the cavity's Q factor to ∼300 during the acceleration phase of the beam. However, when the beam is at store and the FD is removed, the cavity is excited by both the yellow and the blue beams at 2 x 0.3A to attain the required 2MV voltage across its gap. The cavity then is operated to increase the luminosity of the RHIC experiments. Table 1 lists the parameters of the FD. Figure 1 shows the configuration of the FD fully inserted into the 56MHz SRF cavity; this complete insertion is defined as the start location (0cm) of FD simulation, an assumption we make throughout this paper. The power consumed by the cavity while maintaining the beam's energy and its orbit is compensated by the 28MHz accelerating cavities in the storage ring. The power dissipation of the external load is dynamic with respect to the position of the FD during its extraction. As a function of the external Q and the EM field in the cavity, the power should peak with the FD at a certain vertical location. Our calculation of the power extracted is detailed in the following sections. Figure 2 plots the frequency change in the cavity, and the external Q against the changes in position of the FD. The location of the FD is selected carefully such that the frequency will approach the designed working point from the lower side only. The loaded Q of the cavity is 223 when the FD is fully

  11. Design and commissioning of Fermilab's vertical test stand for ILC SRF cavities.

    Energy Technology Data Exchange (ETDEWEB)

    Ozelis, Joseph P.; Carcagno, Ruben; Ginsburg, Camille M.; Huang, Yuenian; Norris, Barry; Peterson, Thomas; Poloubotko, Valeri; Rabehl, roger; Rakhno, Igor; Reid, Clark; Sergatskov, Dmitri A.; /Fermilab

    2007-06-01

    As part of its ILC program, Fermilab is developing a facility for vertical testing of SRF cavities. It operates at a nominal temperature of 2K, using a cryoplant that can supply LHe in excess of 20g/sec and provide bath pumping capacity of 125W at 2K. The below-grade cryostat consists of a vacuum vessel and LHe vessel, equipped with magnetic shielding to reduce the ambient magnetic field to <10mG. Internal fixed and external movable radiation shielding ensures that exposure to personnel is minimized. The facility features an integrated personnel safety system consisting of RF switches, interlocks, and area radiation monitors.

  12. Design and commissioning of Fermilab's vertical test stand for ILC SRF cavities

    International Nuclear Information System (INIS)

    Ozelis, Joseph P.; Carcagno, Ruben; Ginsburg, Camille M.; Huang, Yuenian; Norris, Barry; Peterson, Thomas; Poloubotko, Valeri; Rabehl, roger; Rakhno, Igor; Reid, Clark; Sergatskov, Dmitri A.

    2007-01-01

    As part of its ILC program, Fermilab is developing a facility for vertical testing of SRF cavities. It operates at a nominal temperature of 2K, using a cryoplant that can supply LHe in excess of 20g/sec and provide bath pumping capacity of 125W at 2K. The below-grade cryostat consists of a vacuum vessel and LHe vessel, equipped with magnetic shielding to reduce the ambient magnetic field to <10mG. Internal fixed and external movable radiation shielding ensures that exposure to personnel is minimized. The facility features an integrated personnel safety system consisting of RF switches, interlocks, and area radiation monitors

  13. Tuner control system of Spoke012 SRF cavity for C-ADS injector I

    Science.gov (United States)

    Liu, Na; Sun, Yi; Wang, Guang-Wei; Mi, Zheng-Hui; Lin, Hai-Ying; Wang, Qun-Yao; Liu, Rong; Ma, Xin-Peng

    2016-09-01

    A new tuner control system for spoke superconducting radio frequency (SRF) cavities has been developed and applied to cryomodule I of the C-ADS injector I at the Institute of High Energy Physics, Chinese Academy of Sciences. We have successfully implemented the tuner controller based on Programmable Logic Controller (PLC) for the first time and achieved a cavity tuning phase error of ±0.7° (about ±4 Hz peak to peak) in the presence of electromechanical coupled resonance. This paper presents preliminary experimental results based on the PLC tuner controller under proton beam commissioning. Supported by Proton linac accelerator I of China Accelerator Driven sub-critical System (Y12C32W129)

  14. Characterization of Nb SRF cavity materials by white light interferometry and replica techniques

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Chen [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); The Applied Science Department, The College of William and Mary, Williamsburg, VA 23185 (United States); Reece, Charles [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Kelley, Michael, E-mail: mkelley@jlab.org [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); The Applied Science Department, The College of William and Mary, Williamsburg, VA 23185 (United States)

    2013-06-01

    Much work has shown that the topography of the interior surface is an important contributor to the performance of Nb superconducting radiofrequency (SRF) accelerator cavities. Micron-scale topography is implicated in non-linear loss mechanisms that limit the useful accelerating gradient range and impact cryogenic cost. Aggressive final chemical treatments in cavity production seek to reliably obtain “smoothest” surfaces with superior performance. Process development suffers because the cavity interior surface cannot be viewed directly without cutting out pieces, rendering the cavities unavailable for further study. Here we explore replica techniques as an alternative, providing imprints of cavity internal surface that can be readily examined. A second matter is the topography measurement technique used. Atomic force microscopy (AFM) has proven successful, but too time intensive for routine use in this application. We therefore introduce white light interferometry (WLI) as an alternative approach. We examined real surfaces and their replicas, using AFM and WLI. We find that the replica/WLI is promising to provide the large majority of the desired information, recognizing that a trade-off is being made between best lateral resolution (AFM) and the opportunity to examine much more surface area (WLI).

  15. Development of an advanced electropolishing setup for multicell high gradient niobium cavities

    Directory of Open Access Journals (Sweden)

    F. Éozénou

    2012-08-01

    Full Text Available Reproducible operation at high performances of superconducting cavities is required for linear accelerators. High beta elliptical cavities are thus of concern and, to achieve required performances for such resonators, surface preparation including electropolishing is recommended. We have designed and operate a setup for electropolishing in the vertical position of multicell cavities in order to: (i obtain high yield with large elliptical cavities for Superconducting Linac (SPL or European Spallation Source projects; (ii develop a reference installation demonstrating that this process is appropriate for the large scale treatment of cavities in industry. The setup described here is the first one able to electropolish vertically multicell cavities with circulating acid and high safety standards. This equipment makes it possible to use a wide range of parameters such as voltage, acid flow rate, temperature, and nitrogen injection with an R&D purpose in mind. Optimization is studied using modeling with COMSOL software for different cavities. As examples, we present some results for the 704 MHz high-beta SPL cavity and the 1300 MHz International Linear Collider cavity and show the influence of cathode shape on both acid flow and electric field distribution during the process. Importance of the size of the cavity and first results achieved on single-cell and nine-cell cavities will be discussed.

  16. Continued conditioning of the Fermilab 400 MeV linac high-gradient side-coupled cavities

    International Nuclear Information System (INIS)

    Kroc, Thomas; McCrory, Elliott; Moretti, Alfred; Popovic, Milorad

    1996-01-01

    The high-energy portion of the Fermilab 400 MeV Linac is made of high gradient (37 MV/meter surface field) side-coupled cavity sections which were conditioned over a 10 month period before their installation in August of 1993. We have continued to monitor the conditioning of these cavities since that time while the cavities have been in operation, and those results are presented here. The sparking rate and the X-ray production are measured and compared with the 1992/3 pre-operational and 1993/4 early operational measurements. These rates are consistent with a continued diminishing of these phenomena. Predictions and spark management strategies presented in earlier reports are evaluated in light of present experiences. We also have been measuring the sparking rate within this structure with and without our 50 mA peak beam. We find that the sparking rate is 20% higher with beam in the accelerator. (author)

  17. Design of 650 MHz, β=0.61, 5-cell SRF cavity and development of single cell niobium cavity

    International Nuclear Information System (INIS)

    Seth, Sudeshna; Som, Sumit; Bhattacharyya, Pranab

    2015-01-01

    In India, DAE laboratories and other institutes are now actively involved in research and development activities on SRF cavities and associated technologies for the proposed high current, high energy proton linear accelerators like ISNS/IADS and also for the FERMILAB PIP-II program under Indian institutions-Fermilab collaboration (IIFC). As part of the above activities, VECC, Kolkata, has been involved in the design, analysis and development of a 650 MHz, β=0.61, 5-cell elliptical shape Superconducting RF linac cavity. RF design involves optimization of the geometry to get acceptable values of field enhancement factors (magnetic and electric), R/Q , Geometric factor, coupling factor and field flatness. This paper describes the RF design using 2-D superfish and 3-D CST Microwave studio and multipacting analysis using 2-D Multipac2.1 and 3-D CST Particle Studio. A prototype 1-cell aluminum cavity and a prototype 5-cell copper cavity have been fabricated using die-punch assembly designed for fabrication of elliptical half-cells to check the procedures for forming and to make sure the desired frequency and field flatness could be obtained. RF characterization has been carried out for both the prototypes using Vector Network Analyzer and Bead pull measurement set up.The fabrication of a single-cell niobium cavity has been carried out indigenously and with the help of Electron Beam Welding (EBW) facility at IUAC, New Delhi. CMM measurement and RF characterization of the niobium half cells and full cell cavities have been carried out. This paper describes the development and measurement of prototype cavities and single cell niobium cavity. (author)

  18. Improving the work function of the niobium surface of SRF cavities by plasma processing

    International Nuclear Information System (INIS)

    Tyagi, P.V.; Doleans, M.; Hannah, B.; Afanador, R.; McMahan, C.; Stewart, S.; Mammosser, J.; Howell, M.; Saunders, J.; Degraff, B.; Kim, S.-H.

    2016-01-01

    Highlights: • An in situ plasma processing for SNS SRF cavities has been developed to remove hydrocarbons from cavity surface. • Reactive oxygen plasma is very effective to remove hydrocarbons from niobium top surface. • Reactive oxygen plasma processing increases the work function of niobium surface in the range of 0.5–1.0 eV. • It was observed that hydrocarbons can migrate at plasma cleaned top surface from near surface regions when waiting in vacuum at room temperature. • Multiple cycles of plasma processing with waiting periods in between was found beneficial to mitigate such hydrocarbons migration at plasma cleaned surface. - Abstract: An in situ plasma processing technique using chemically reactive oxygen plasma to remove hydrocarbons from superconducting radio frequency cavity surfaces at room temperature has been developed at the spallation neutron source, at Oak Ridge National Laboratory. To understand better the interaction between the plasma and niobium surface, surface studies on small samples were performed. In this article, we report the results from those surface studies. The results show that plasma processing removes hydrocarbons from top surface and improves the surface work function by 0.5–1.0 eV. Improving the work function of RF surface of cavities can help to improve their operational performance.

  19. SRF cavity alignment detection method using beam-induced HOM with curved beam orbit

    Science.gov (United States)

    Hattori, Ayaka; Hayano, Hitoshi

    2017-09-01

    We have developed a method to obtain mechanical centers of nine cell superconducting radio frequency (SRF) cavities from localized dipole modes, that is one of the higher order modes (HOM) induced by low-energy beams. It is to be noted that low-energy beams, which are used as alignment probes, are easy to bend in fringe fields of accelerator cavities. The estimation of the beam passing orbit is important because only information about the beam positions measured by beam position monitors outside the cavities is available. In this case, the alignment information about the cavities can be obtained by optimizing the parameters of the acceleration components over the beam orbit simulation to consistently represent the position of the beam position monitors measured at every beam sweep. We discuss details of the orbit estimation method, and estimate the mechanical center of the localized modes through experiments performed at the STF accelerator. The mechanical center is determined as (x , y) =(0 . 44 ± 0 . 56 mm , - 1 . 95 ± 0 . 40 mm) . We also discuss the error and the applicable range of this method.

  20. Investigations of Residual Stresses and Mechanical Properties of Single Crystal Niobium for SRF Cavities

    Science.gov (United States)

    Gnäupel-Herold, Thomas; Myneni, Ganapati Rao; Ricker, Richard E.

    2007-08-01

    This work investigates properties of large grained, high purity niobium with respect to the forming of superconducting radio frequency (SRF) cavities from such large grained sheets. The yield stresses were examined using tensile specimens that were essentially single crystals in orientations evenly distributed in the standard projection triangle. No distinct yield anisotropy was found, however, vacuum annealing increased the yield strength by a factor 2…3. The deep drawing forming operation of the half cells raises the issues of elastic shape changes after the release of the forming tool (springback) and residual stresses, both of which are indicated to be negligible. This is a consequence of the low yield stress (sheet metal forming). However, the significant anisotropy of the transversal plastic strains after uniaxial deformation points to potentially critical thickness variations for large grained / single crystal half cells, thus raising the issue of controlling grain orientation or using single crystal sheet material.

  1. A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

    Science.gov (United States)

    Tian, Hui; Ribeill, Guilhem; Xu, Chen; Reece, Charles E.; Kelley, Michael J.

    2011-03-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

  2. A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

    International Nuclear Information System (INIS)

    Tian Hui; Ribeill, Guilhem; Xu Chen; Reece, Charles E.; Kelley, Michael J.

    2011-01-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

  3. Experimental and Numerical Analysis of Hydroformed Tubular Materials for Superconducting Radio Frequency (SRF) Cavities

    Science.gov (United States)

    Kim, Hyun Sung

    Superconducting radio frequency (SRF) cavities represent a well established technology benefiting from some 40 years of research and development. An increasing demand for electron and positron accelerators leads to a continuing interest in improved cavity performance and fabrication techniques. Therefore, several seamless cavity fabrication techniques have been proposed for eliminating the multitude of electron-beam welded seams that contribute to the introduction of performance-reducing defects. Among them, hydroforming using hydraulic pressure is a promising fabrication technique for producing the desired seamless cavities while at the same time reducing manufacturing cost. This study focused on experimental and numerical analysis of hydroformed niobium (Nb) tubes for the successful application of hydroforming technique to the seamless fabrication of multi-cell SRF cavities for particle acceleration. The heat treatment, tensile testing, and bulge testing of Cu and Nb tubes has been carried out to both provide starting data for models of hydroforming of Nb tube into seamless SRF cavities. Based on the results of these experiments, numerical analyses using finite element modeling were conducted for a bulge deformation of Cu and Nb. In the experimental part of the study samples removed from representative tubes were prepared for heat treatment, tensile testing, residual resistance ratio (RRR) measurement, and orientation imaging electron microscopy (OIM). After being optimally heat treated Cu and Nb tubes were subjected to hydraulic bulge testing and the results analyzed. For numerical analysis of hydroforming process, two different simulation approaches were used. The first model was the macro-scale continuum model using the constitutive equations (stress-strain relationship) as an input of the simulation. The constitutive equations were obtained from the experimental procedure including tensile and tube bulge tests in order to investigate the influence of loading

  4. Surface polishing of niobium for superconducting radio frequency (SRF) cavity applications

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Liang [College of William and Mary, Williamsburg, VA (United States)

    2014-08-01

    Niobium cavities are important components in modern particle accelerators based on superconducting radio frequency (SRF) technology. The interior of SRF cavities are cleaned and polished in order to produce high accelerating field and low power dissipation on the cavity wall. Current polishing methods, buffered chemical polishing (BCP) and electro-polishing (EP), have their advantages and limitations. We seek to improve current methods and explore laser polishing (LP) as a greener alternative of chemical methods. The topography and removal rate of BCP at different conditions (duration, temperature, sample orientation, flow rate) was studied with optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Differential etching on different crystal orientations is the main contributor to fine grain niobium BCP topography, with gas evolution playing a secondary role. The surface of single crystal and bi-crystal niobium is smooth even after heavy BCP. The topography of fine grain niobium depends on total removal. The removal rate increases with temperature and surface acid flow rate within the rage of 0~20 °C, with chemical reaction being the possible dominate rate control mechanism. Surface flow helps to regulate temperature and avoid gas accumulation on the surface. The effect of surface flow rate on niobium EP was studied with optical microscopy, atomic force microscopy (AFM), and power spectral density (PSD) analysis. Within the range of 0~3.7 cm/s, no significant difference was found on the removal rate and the macro roughness. Possible improvement on the micro roughness with increased surface flow rate was observed. The effect of fluence and pulse accumulation on niobium topography during LP was studied with optical microscopy, SEM, AFM, and PSD analysis. Polishing on micro scale was achieved within fluence range of 0.57~0.90 J/cm2, with pulse accumulation adjusted accordingly. Larger area treatment was proved possible by

  5. Development of Nb$_3$Sn coatings by magnetron sputtering for SRF cavities

    CERN Document Server

    Rosaz, G.; Leaux, F.; Motschmann, F.; Mydlarz, Z.; Taborelli, M.; Vollenberg, W.

    2016-01-01

    Cost and energy savings are an integral requirement in the design of future particle accelerators. Very low losses SRF accelerating systems, together with high-efficiency cryogenics systems, have the potential of low running costs. The association to the capital cost reduction allowed by thin films coated copper cavities may represent the best overall cost-performance compromise. This strategy has been applied for instance in LEP, the LHC and HIE-ISOLDE with the niobium thin films technology. New materials must be considered to improve the quality factor of the cavities, such as Nb$_{3}$Sn, which could also ideally operate at higher temperature thus allowing further energy savings. The study considers the possibility to coat a copper resonator with an Nb$_{3}$Sn layer by means of magnetron sputtering using an alloyed target. We present the impact of the process parameters on the as-deposited layer stoichiometry. The latter is in good agreement with previous results reported in the literature and can be tuned ...

  6. High-Q, high gradient niobium-coated cavities at CERN

    CERN Document Server

    Calatroni, Sergio; Darriulat, Pierre; Peck, M A; Valente, A M; Van't Hof, C A

    1999-01-01

    Superconducting cavities made by sputter-deposition of a thin niobium film onto copper have proven over the years to be a viable alternative to bulk niobium, the best example being the very successful operation of LEP at 200 GeV. It will be shown that this technology, investigated at 1.5 GHz by a dedicated R&D effort at CERN, can be developed to unprecedented performance, proving that no fundamental limitation prevents high quality factors to be maintained over a broad range of accelerating field.

  7. Materials and surface aspects in the development of SRF Niobium cavities

    CERN Document Server

    Antoine, C

    2012-01-01

    Foreword from author; When I joined the CEA Saclay SRF group in 1989, my initial background was physical chemistry and surface science, which I completed later on with solid state physics and metallurgy. Most accelerator physicists at that time had training in RF, plasma physics, nuclear or particle physics. We were very few with a background in material science. Working with people with a different background than yours reveals to be both challenging and funny: you can impress them with things you consider basic while they simply do not believe you for other things you consider so well admitted that you do not even remember where it comes from. At the end it obliges you to reconsider your basics and re-question many results, which opens many new and sometimes unexpected paths. Like usual in science, answering one question rises many new ones, and trying to improve cavities performance led to fascinating physics problems. Exploring some of these problems often requires techniques and expertise that are far be...

  8. Full Characterization at Low Temperature of Piezoelectric Actuators Used for SRF Cavities Active Tuning

    CERN Document Server

    Fouaidy, Mohammed; Chatelet, Frederic; Hammoudi, Nourredine; Martinet, Guillaume; Olivier, Aurelia; Saugnac, Herve

    2005-01-01

    In the frame of the CARE project activities, supported by EU, IPN Orsay participate to the development of a fast cold tuning system for SRF cavities operating at a temperature T=2 K. The study is aimed at full characterization of piezoelectric actuators at low temperature. A new experimental facility was developed for testing various prototypes piezoelectric actuators and successfully operated for T in the range 1.8 K-300 K. Different parameters were investigated as function of T: piezoelectric actuator displacement vs. applied voltage V, capacitance vs. T, dielectric and thermal properties vs. T and finally heating DT due to dielectric losses vs. modulating voltage Vmod and frequency. We observed a decrease of the Full Range Displacement (FRD or DX) of the actuator from ~40μm @ 300K down to 1.8μm-3μm @ 1.8K, depending on both material and fabrication process of the piezostacks. Besides, both material and fabrication process have a strong influence on the shape of the characteris...

  9. Surface studies of niobium chemically polished under conditions for superconducting radio frequency (SRF) cavity production

    Science.gov (United States)

    Tian, Hui; Reece, Charles E.; Kelley, Michael J.; Wang, Shancai; Plucinski, Lukasz; Smith, Kevin E.; Nowell, Matthew M.

    2006-11-01

    The performance of niobium superconducting radiofrequency (SRF) accelerator cavities is strongly impacted by the topmost several nanometers of the active (interior) surface, especially as influenced by the final surface conditioning treatments. We examined the effect of the most commonly employed treatment, buffered chemical polishing (BCP), on polycrystalline niobium sheet over a range of realistic solution flow rates using electron back scatter diffraction (EBSD), stylus profilometry, atomic force microscopy, laboratory XPS and synchrotron (variable photon energy) XPS, seeking to collect statistically significant datasets. We found that the predominant general surface orientation is (1 0 0), but others are also present and at the atomic-level details of surface plane orientation are more complex. The post-etch surface exhibits micron-scale roughness, whose extent does not change with treatment conditions. The outermost surface consists of a few-nm thick layer of niobium pentoxide, whose thickness increases with solution flow rate to a maximum of 1.3-1.4 times that resulting from static solution. The standard deviation of the roughness measurements is ±30% and that of the surface composition is ±5%.

  10. Surface studies of niobium chemically polished under conditions for superconducting radio frequency (SRF) cavity production

    Energy Technology Data Exchange (ETDEWEB)

    Tian Hui [Thomas Jefferson National Accelerator Facility and College of William and Mary (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility and College of William and Mary (United States); Kelley, Michael J. [Thomas Jefferson National Accelerator Facility and College of William and Mary (United States)]. E-mail: mkelley@jlab.org; Wang Shancai [Department of Physics, Boston University (United States); Plucinski, Lukasz [Department of Physics, Boston University (United States); Smith, Kevin E. [Department of Physics, Boston University (United States); Nowell, Matthew M. [EDAX TSL (United States)

    2006-11-30

    The performance of niobium superconducting radiofrequency (SRF) accelerator cavities is strongly impacted by the topmost several nanometers of the active (interior) surface, especially as influenced by the final surface conditioning treatments. We examined the effect of the most commonly employed treatment, buffered chemical polishing (BCP), on polycrystalline niobium sheet over a range of realistic solution flow rates using electron back scatter diffraction (EBSD), stylus profilometry, atomic force microscopy, laboratory XPS and synchrotron (variable photon energy) XPS, seeking to collect statistically significant datasets. We found that the predominant general surface orientation is (1 0 0), but others are also present and at the atomic-level details of surface plane orientation are more complex. The post-etch surface exhibits micron-scale roughness, whose extent does not change with treatment conditions. The outermost surface consists of a few-nm thick layer of niobium pentoxide, whose thickness increases with solution flow rate to a maximum of 1.3-1.4 times that resulting from static solution. The standard deviation of the roughness measurements is {+-}30% and that of the surface composition is {+-}5%.

  11. Surface Studies of Niobium Chemically Polished Under Conditions for Superconducting Radio Frequency (SRF) Cavity Production

    Energy Technology Data Exchange (ETDEWEB)

    Tian,H.; Reece, C.; Kelley, M.; Wang, S.; Plucinski, L.; Smith, K.; Nowell, M.

    2006-01-01

    The performance of niobium superconducting radiofrequency (SRF) accelerator cavities is strongly impacted by the topmost several nanometers of the active (interior) surface, especially as influenced by the final surface conditioning treatments. We examined the effect of the most commonly employed treatment, buffered chemical polishing (BCP), on polycrystalline niobium sheet over a range of realistic solution flow rates using electron back scatter diffraction (EBSD), stylus profilometry, atomic force microscopy, laboratory XPS and synchrotron (variable photon energy) XPS, seeking to collect statistically significant datasets. We found that the predominant general surface orientation is (1 0 0), but others are also present and at the atomic-level details of surface plane orientation are more complex. The post-etch surface exhibits micron-scale roughness, whose extent does not change with treatment conditions. The outermost surface consists of a few-nm thick layer of niobium pentoxide, whose thickness increases with solution flow rate to a maximum of 1.3-1.4 times that resulting from static solution. The standard deviation of the roughness measurements is {+-}30% and that of the surface composition is {+-}5%.

  12. Investigations of Residual Stresses and Mechanical Properties of Single Crystal Niobium for SRF Cavities

    International Nuclear Information System (INIS)

    Gnaeupel-Herold, Thomas; Myneni, Ganapati Rao; Ricker, Richard E.

    2007-01-01

    This work investigates properties of large grained, high purity niobium with respect to the forming of superconducting radio frequency (SRF) cavities from such large grained sheets. The yield stresses were examined using tensile specimens that were essentially single crystals in orientations evenly distributed in the standard projection triangle. No distinct yield anisotropy was found, however, vacuum annealing increased the yield strength by a factor 2...3. The deep drawing forming operation of the half cells raises the issues of elastic shape changes after the release of the forming tool (springback) and residual stresses, both of which are indicated to be negligible. This is a consequence of the low yield stress (< 100 MPa) and the large thickness (compared to typical thicknesses in sheet metal forming). However, the significant anisotropy of the transversal plastic strains after uniaxial deformation points to potentially critical thickness variations for large grained / single crystal half cells, thus raising the issue of controlling grain orientation or using single crystal sheet material

  13. Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma

    Science.gov (United States)

    Upadhyay, J.; Palczewski, A.; Popović, S.; Valente-Feliciano, A.-M.; Im, Do; Phillips, H. L.; Vušković, L.

    2017-12-01

    An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF) accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity's inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.

  14. Development of Vertical Buffered Electropolishing for Its Post-Treatment Technology on 1.5 GHz Niobium SRF Cavities

    International Nuclear Information System (INIS)

    Jin Song; Lu Xiang-Yang; Lin Lin; Zhao Kui; Wu, A. T.; Rimmer, R. A.

    2011-01-01

    We report the latest research development of vertical buffered electropolishing on its post-treatment procedure as well as the effects of several major post-treatment techniques for buffered electropolishing (BEP) processed 1.5 GHz niobium (Nb) superconducting radio frequency (SRF) cavities. With the established post-treatment procedure, an accelerating gradient of 28.4 MV/m is obtained on a single cell cavity of the cebaf shape. This is the best result in the history of BEP development. The cavity is limited by quench with a high quality factor over 1.2 × 10 10 at the quench point. Analyses from optical inspection and temperature-mapping show that the quench should be originated from the pits that were already present on the cavity before this BEP treatment. All of these factors indicate that this procedure will have a great potential to produce better results if cavities without intrinsic performance limiting imperfections are used. (nuclear physics)

  15. A high gradient test of a single-cell superconducting radio frequency cavity with a feedback waveguide

    Science.gov (United States)

    Kostin, Roman; Avrakhov, Pavel; Kanareykin, Alexei; Solyak, Nikolay; Yakovlev, Vyacheslav; Kazakov, Sergey; Wu, Genfa; Khabiboulline, Timergali; Rowe, Allan; Rathke, John

    2015-09-01

    The most severe problem of the international linear collider (ILC-type) is its high cost, resulting in part from the enormous length of the collider. This length is determined mainly by the achievable accelerating gradient in the RF system of the collider. In current technology, the maximum acceleration gradient in superconducting (SC) structures is determined mainly by the value of the surface RF magnetic field. In order to increase the gradient, a superconducting traveling wave accelerating (STWA) structure is suggested. Utilization of STWA structure with small phase advance per cell for future high energy linear colliders such as ILCs may provide an accelerating gradient 1.2-1.4 times larger [1] than a standing wave structure. However, STWA structure requires a feedback waveguide for power redirecting from the end of the structure back to the front end of accelerating structure. Recent tests of a 1.3 GHz model of a single-cell cavity with waveguide feedback demonstrated an accelerating gradient comparable to the gradient of a single-cell ILC-type cavity from the same manufacturer [2]. In the present paper, high gradient test results are presented.

  16. Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma

    Directory of Open Access Journals (Sweden)

    J. Upadhyay

    2017-12-01

    Full Text Available An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity’s inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.

  17. New Insights into the Limitations on the Efficiency and Achievable Gradients in Nb3Sn SRF Cavities

    Science.gov (United States)

    Hall, Daniel Leslie

    The A15 superconductor Nb3Sn has shown great promise to replace niobium as the material of choice for the construction of superconducting radio-frequency (SRF) accelerator cavities. It promises, at least on paper, greater efficiency and higher accelerating gradients, with the potential to enable the construction of smaller yet more powerful accelerators than can be constructed using niobium. Although the state-of-the-art performance of cavities coated with Nb3Sn has shown great potential, the achievable limits in cavity quality factor Q0 and accelerating gradient Eacc are still below that expected given theoretical limits. In this work we present and discuss results of experiments carried out to understand the current limitations on Q0 and Eacc, and propose methods to improve these further. We will conclude with an outlook to the future, and the prospects that Nb3Sn could enable.

  18. Improvement of the operational performance of SRF cavities via in situ helium processing and waveguide vacuum processing

    International Nuclear Information System (INIS)

    Reece, C.E.; Drury, M.; Rao, M.G.; Nguyen-Tuong, V.

    1997-01-01

    The useful performance range of the superconducting rf (SRF) cavities in the CEBAF accelerator at Jefferson Lab is frequently limited by electron field emission and derived phenomena. Improvements are required to support future operation of the accelerator at higher than 5 GeV. Twelve operational cryomodules have been successfully processed to higher useful operating gradients via rf-helium processing. Progress against field emission was evidenced by improved high-field Q, reduced x-ray production and greatly reduced incidence of arcing at the cold ceramic window. There was no difficulty reestablishing beamline vacuum following the processing. Cavities previously limited to 4-6 MV/m are now operating stably at 6-9 MV/m. By applying a pulsed-rf processing technique, we have also improved the pressure stability of the thermal transition region of the input waveguide for several cavities

  19. Fabrication and Final Field Tuning of Copper Cavity Models for a High-Current SRF ERL at 703.75 MHz

    CERN Document Server

    Cole, Michael; Burger, Al; Falletta, Michael; Holmes, Douglas; Peterson, Ed; Wong, Robert

    2005-01-01

    Advanced Energy Systems is currently under contract to BNL to fabricate a five cell superconducting cavity and cryomodule for the RHIC eCooler SRF Energy Recovery Linac (ERL) program.* The cavity is designed and optimized for ampere class SRF ERL service. As part of this program, we have fabricated two low power copper models of the RF cavities. During the fabrication process a series of frequency measurements were made and compared to the frequency expected at that point in the fabrication process. Where possible, the cavity was modified either before or during, the next fabrication step to tune the cavity frequency toward the target frequency. Following completion of the cavities they were tuned for field flatness and frequency. This paper will review the measurements made, frequency tuning performed, and discuss discrepancies between the expected and measured results. We will also review the as fabricated field profiles and the results of the tuning steps. Further, the cost and benefits of extensive in pro...

  20. Modified 3½-Cell SC Cavity Made of Large Grain Niobium for the FZD SRF Photoinjector

    CERN Document Server

    Murcek, P; Michel, P; Moeller, K; Arnold, A; Teichert, J; Xiang, R; Freitag, M; Kneisel, P

    2010-01-01

    An SRF photoinjector has been successfully tested in FZD under the collaboration of BESSY, DESY, FZD, and MBI. In order to improve the gun cavity quality and thus reach a higher gradient, a new 3+1/2 superconducting cavity is being fabricated in cooperation with JLab. The modified cavity is made of large grain niobium, composed of one filter choke, one special designed half-cell (gun-cell) and three TESLA cavities. In this paper, the main updates of the new cavity design will be explained in detail. The deformation of the filter choke and the gun-cell, which is caused by pressure fluctuation in the He-line and also by the effect of the Lorentz force, will be minimized by stiffening between the filter choke and the gun-cell. Meanwhile, the cathode hole in the choke and gun-cell is enlarged for better rinsing. To simplify assembly, the NbTi pick-up will be welded directly on the wall of filter choke.

  1. Superconducting Radiofrequency (SRF) Acceleration Technology

    Data.gov (United States)

    Federal Laboratory Consortium — SRF cavities enable accelerators to increase particle beam energy levels while minimizing the use of electrical power by all but eliminating electrical resistance....

  2. Design, Construction, and Initial Test of High Spatial Resolution Thermometry Arrays for Detection of Surface Temperature Profiles on SRF Cavities in Super Fluid Helium

    Energy Technology Data Exchange (ETDEWEB)

    Ari Palczewski, Rongli Geng, Grigory Eremeev

    2011-07-01

    We designed and built two high resolution (0.6-0.55mm special resolution [1.1-1.2mm separation]) thermometry arrays prototypes out of the Allen Bradley 90-120 ohm 1/8 watt resistor to measure surface temperature profiles on SRF cavities. One array was designed to be physically flexible and conform to any location on a SRF cavity; the other was modeled after the common G-10/stycast 2850 thermometer and designed to fit on the equator of an ILC (Tesla 1.3GHz) SRF cavity. We will discuss the advantages and disadvantages of each array and their construction. In addition we will present a case study of the arrays performance on a real SRF cavity TB9NR001. TB9NR001 presented a unique opportunity to test the performance of each array as it contained a dual (4mm separation) cat eye defect which conventional methods such as OST (Oscillating Superleak second-sound Transducers) and full coverage thermometry mapping were unable to distinguish between. We will discuss the new arrays ability to distinguish between the two defects and their preheating performance.

  3. Fabrication and Testing of the SRF Cavities for the CEBAF 12 GeV Upgrade Prototype Cryomodule Renascence

    International Nuclear Information System (INIS)

    Charles Reece; Edward Daly; Stephen Manning; Robert Manus; Samuel Morgan; Joseph Ozelis; Larry Turlington

    2005-01-01

    Twelve seven-cell niobium cavities for the CEBAF 12 GeV upgrade prototype cryomodule Renascence have been fabricated at JLab and tested individually. This set includes four of the ''Low Loss'' (LL) design and eight of the ''High Gradient'' (HG) design. The fabrication strategy was an efficient mix of batch job-shop component machining and in-house EBW, chemistry, and final-step machining to meet mechanical tolerances. Process highlights will be presented. The cavities have been tested at 2.07 K, the intended CEBAF operating temperature. Performance exceeded the tentative design requirement of 19.2 MV/m cw with less than 29 W dynamic heat dissipation. These results, as well as the HOM damping performance will be presented

  4. Fabrication and Testing of the SRF cavities for the CEBAF 12 GeV Upgrade Prototype Cryomodule Renascence

    International Nuclear Information System (INIS)

    C. E. Reece; E. F. Daly; S. Manning; R. Manus; S. Morgan; J. P. Ozelis; L. Turlington

    2005-01-01

    Twelve seven-cell niobium cavities for the CEBAF 12 GeV upgrade prototype cryomodule Renascence have been fabricated at JLab and tested individually. This set includes four of the ''Low Loss'' (LL) design and eight of the ''High Gradient'' (HG) design. The fabrication strategy was an efficient mix of batch job-shop component machining and in-house EBW, chemistry, and final-step machining to meet mechanical tolerances. Process highlights will be presented. The cavities have been tested at 2.07 K, the intended CEBAF operating temperature. Performance exceeded the tentative design requirement of 19.2 MV/m CW with less than 29 W dynamic heat dissipation. These results, as well as the HOM damping performance are presented

  5. Study of Nb-Cu 1.3 GHz SRF cavity resonators for future particle accelerators

    CERN Document Server

    Amelin, Kirill

    2017-01-01

    Niobium-coated superconducting radio-frequency cavities have a number of advantages over cavities made from bulk niobium. Cavities coated with high-power impulse magnetron sputtering are tested at CERN in order to optimize the coating and study the Q-slope that limits the performance. To accurately measure the quality factor as a function of accelerating field, it is important to have good matching between an input antenna and a cavity impedance. To improve the matching, a variable coupler that changes the length of the antenna can be used. We have shown that the Q-factor of the input antenna can be changed between $10^7-10^{11}$ by moving the antenna, which should allow to achieve critical coupling with a cavity. This technology could be used in future measurements, so that reflections are always minimized.

  6. Compensating microphonics in SRF cavities to ensure beam stability for future free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Axel

    2008-07-21

    In seeded High-Gain-Harmonic-Generation free electron lasers or energy recovery linear accelerators the requirements for the bunch-to-bunch timing and energy jitter of the beam are in the femtosecond and per mill regime. This implies the ability to control the cavity radiofrequency (RF) field to an accuracy of 0.02 in phase and up to 1.10{sup -4} in amplitude. For the planned BESSY-FEL it is envisaged to operate 144 superconducting 1.3 GHz cavities of the 2.3 GeV driver linac in continuous wave mode and at a low beam current. The cavity resonance comprises a very narrow bandwidth of the order of tens of Hertz. Such cavities have been characterized under accelerator like conditions in the HoBiCaT test facility. It was possible to measure the error sources affecting the field stability in continuous wave (CW) operation. Microphonics, the main error source for a mechanical detuning of the cavities, lead to an average fluctuation of the cavity resonance of 1-5 Hz rms. Furthermore, the static and dynamic Lorentz force detuning and the helium pressure dependance of the cavity resonance have been measured. Single cavity RF control and linac bunch-to-bunch longitudinal phase space modeling containing the measured properties showed, that it is advisable to find means to minimize the microphonics detuning by mechanical tuning. Thus, several fast tuning systems have been tested for CW operation. These tuners consist of a motor driven lever for slow and coarse tuning and a piezo that is integrated into the tuner support for fast and fine tuning. Regarding the analysis of the detuning spectrum an adaptive feedforward method based on the least-mean-square filter algorithm has been developed for fast cavity tuning. A detuning compensation between a factor of two and up to a factor of seven has been achieved. Modeling the complete system including the fast tuning scheme, showed that the requirements of the BESSY-FEL are attainable. (orig.)

  7. Compensating microphonics in SRF cavities to ensure beam stability for future free electron lasers

    International Nuclear Information System (INIS)

    Neumann, Axel

    2008-01-01

    In seeded High-Gain-Harmonic-Generation free electron lasers or energy recovery linear accelerators the requirements for the bunch-to-bunch timing and energy jitter of the beam are in the femtosecond and per mill regime. This implies the ability to control the cavity radiofrequency (RF) field to an accuracy of 0.02 in phase and up to 1.10 -4 in amplitude. For the planned BESSY-FEL it is envisaged to operate 144 superconducting 1.3 GHz cavities of the 2.3 GeV driver linac in continuous wave mode and at a low beam current. The cavity resonance comprises a very narrow bandwidth of the order of tens of Hertz. Such cavities have been characterized under accelerator like conditions in the HoBiCaT test facility. It was possible to measure the error sources affecting the field stability in continuous wave (CW) operation. Microphonics, the main error source for a mechanical detuning of the cavities, lead to an average fluctuation of the cavity resonance of 1-5 Hz rms. Furthermore, the static and dynamic Lorentz force detuning and the helium pressure dependance of the cavity resonance have been measured. Single cavity RF control and linac bunch-to-bunch longitudinal phase space modeling containing the measured properties showed, that it is advisable to find means to minimize the microphonics detuning by mechanical tuning. Thus, several fast tuning systems have been tested for CW operation. These tuners consist of a motor driven lever for slow and coarse tuning and a piezo that is integrated into the tuner support for fast and fine tuning. Regarding the analysis of the detuning spectrum an adaptive feedforward method based on the least-mean-square filter algorithm has been developed for fast cavity tuning. A detuning compensation between a factor of two and up to a factor of seven has been achieved. Modeling the complete system including the fast tuning scheme, showed that the requirements of the BESSY-FEL are attainable. (orig.)

  8. Annealing to Mitigate Pitting in Electropolished Niobium Coupons and SRF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Cooley, L.D.; Hahn, E.; Hicks, D.; Romanenko, A.; Schuessler, R.; Thompson, C.; /Fermilab

    2011-06-08

    Ongoing studies at Fermilab investigate whether dislocations and other factors instigate pitting during cavity electropolishing (EP), despite careful processing controls and the inherent leveling mechanism of EP itself. Here, cold-worked niobium coupons, which exhibited increased tendencies for pitting in our past study, were annealed in a high vacuum furnace and subsequently processed by EP. Laser confocal scanning microscopy and special defect counting algorithms were used to assess the population of pits formed. Hardness measurements indicated that annealing for 2 hours at 800 C produced recovery, whereas annealing for 12 hours at 600 C did not, as is consistent with known changes for cavities annealed in a similar way. The 800 C anneal was effective in some cases but not others, and we discuss reasons why tendencies for pitting remain. We discuss implications for cavities and continued work to understand pitting.

  9. Improving the work function of the niobium surface of SRF cavities by plasma processing

    Science.gov (United States)

    Tyagi, P. V.; Doleans, M.; Hannah, B.; Afanador, R.; McMahan, C.; Stewart, S.; Mammosser, J.; Howell, M.; Saunders, J.; Degraff, B.; Kim, S.-H.

    2016-04-01

    An in situ plasma processing technique using chemically reactive oxygen plasma to remove hydrocarbons from superconducting radio frequency cavity surfaces at room temperature has been developed at the spallation neutron source, at Oak Ridge National Laboratory. To understand better the interaction between the plasma and niobium surface, surface studies on small samples were performed. In this article, we report the results from those surface studies. The results show that plasma processing removes hydrocarbons from top surface and improves the surface work function by 0.5-1.0 eV. Improving the work function of RF surface of cavities can help to improve their operational performance.

  10. Conceptual design of a high real-estate gradient cavity for a SRF ERL

    International Nuclear Information System (INIS)

    Xu, Chen; Stony Brook University, NY; Ben-Zvi, Ilan; Stony Brook University, NY; Hao, Yue

    2017-01-01

    The term “real-estate gradient” is used to describe the energy gain provided by an accelerating structure per actual length it takes in the accelerator. given that the length of the tunnel available for the accelerator is constrained, the real-estate gradient is an important measure of the efficiency of a given accelerator structure. When designing an accelerating cavity to be efficient in this sense, the unwanted Higher Order Mode (HOM) fields should be reduced by suitable HOM dampers. This is a particularly important consideration for high current operation. The additional RF components might take longitude space and reduce the total accelerating efficiency. We describe a new high efficiency 5-cell cavity with the dampers included. The total length of the cavity is reduced by 13% as compared to a more conventional design without compromising the cavity fundamental-mode performance. In addition, the HOM impedance is reduced for a higher Beam-Break-Up (BBU) threshold of operating current. In this article, we consider an example, a possible application at the eRHIC Energy Recovery Linac (ERL).

  11. Conceptual design of a high real-estate gradient cavity for a SRF ERL

    Science.gov (United States)

    Xu, Chen; Ben-Zvi, Ilan; Hao, Yue; Xin, Tianmu; Wang, Haipeng

    2017-10-01

    The term "real-estate gradient" is used to describe the energy gain provided by an accelerating structure per actual length it takes in the accelerator. given that the length of the tunnel available for the accelerator is constrained, the real-estate gradient is an important measure of the efficiency of a given accelerator structure. When designing an accelerating cavity to be efficient in this sense, the unwanted Higher Order Mode (HOM) fields should be reduced by suitable HOM dampers. This is a particularly important consideration for high current operation. The additional RF components might take longitude space and reduce the total accelerating efficiency. We describe a new high efficiency 5-cell cavity with the dampers included. The total length of the cavity is reduced by 13% as compared to a more conventional design without compromising the cavity fundamental-mode performance. In addition, the HOM impedance is reduced for a higher Beam-Break-Up (BBU) threshold of operating current. In this paper, we consider an example, a possible application at the eRHIC Energy Recovery Linac (ERL).

  12. Optimizing of the higher order mode dampers in the 56MHz SRF cavity

    International Nuclear Information System (INIS)

    Wu, Q.; Ben-Zvi, I.

    2010-01-01

    Earlier, we reported that a 56 MHz cavity was designed for a luminosity upgrade of the RHIC, and presented the requirements for Higher Order Mode (HOM) damping, the design of the HOM dampers, along with measurements and simulations of the HOM dampers. In this report, we describe our optimization of the dampers performance, and the modifications we made to their original design. We also optimized the number of the HOM dampers, and tested different configurations of locations for them.

  13. Testing of inductive output tube based RF amplifier for 650 MHz SRF cavities

    International Nuclear Information System (INIS)

    Mandal, A.; Som, S.; Manna, S.K.; Ghosh, S.; Seth, S.; Thakur, S.K.; Saha, S.; Panda, U.S.

    2012-01-01

    A 650 MHz IOT based RF amplifier has been developed in VECC. It can be used to power several cavity modules in high energy high current proton linear accelerator to be built for ADSS programme in India and in Project-X at Fermilab, USA. The IOT based amplifier requires different powers supplies, water cooling and forced air cooling for its operation. A Programmable Logic Controller (PLC) based interlocks has been incorporated to take care of systematic on/off of the power supplies and driver amplifier, water flow, air flow and other interlocks for the safe operation of the RF System. In addition to that EPICS based RF operating console and data logging/monitoring system has been added. (author)

  14. Ultimate Gradient Limitation in Niobium Superconducting Accelerating Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Checchin, Mattia [Illinois Inst. of Technology, Chicago, IL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Grassellino, Anna [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Martinello, Martina [Illinois Inst. of Technology, Chicago, IL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Posen, Sam [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Romanenko, Alexander [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Zasadzinski, John [Illinois Inst. of Technology, Chicago, IL (United States)

    2016-06-01

    The present study is addressed to the theoretical description of the ultimate gradient limitation in SRF cavities. Our intent is to exploit experimental data to confirm models which provide feed-backs on how to improve the current state-of-art. New theoretical insight on the cavities limiting factor can be suitable to improve the quench field of N-doped cavities, and therefore to take advantage of high Q0 at high gradients.

  15. Additive manufacturing method for SRF components of various geometries

    Science.gov (United States)

    Rimmer, Robert; Frigola, Pedro E; Murokh, Alex Y

    2015-05-05

    An additive manufacturing method for forming nearly monolithic SRF niobium cavities and end group components of arbitrary shape with features such as optimized wall thickness and integral stiffeners, greatly reducing the cost and technical variability of conventional cavity construction. The additive manufacturing method for forming an SRF cavity, includes atomizing niobium to form a niobium powder, feeding the niobium powder into an electron beam melter under a vacuum, melting the niobium powder under a vacuum in the electron beam melter to form an SRF cavity; and polishing the inside surface of the SRF cavity.

  16. Automated Surface Classification of SRF Cavities for the Investigation of the Influence of Surface Properties onto the Operational Performance

    International Nuclear Information System (INIS)

    Wenskat, Marc

    2015-07-01

    Superconducting niobium radio-frequency cavities are fundamental for the European XFEL and the International Linear Collider. To use the operational advantages of superconducting cavities, the inner surface has to fulfill quite demanding requirements. The surface roughness and cleanliness improved over the last decades and with them, the achieved maximal accelerating field. Still, limitations of the maximal achieved accelerating field are observed, which are not explained by localized geometrical defects or impurities. The scope of this thesis is a better understanding of these limitations in defect free cavities based on global, rather than local, surface properties. For this goal, more than 30 cavities underwent subsequent surface treatments, cold RF tests and optical inspections within the ILC-HiGrade research program and the XFEL cavity production. An algorithm was developed which allows an automated surface characterization based on an optical inspection robot. This algorithm delivers a set of optical surface properties, which describes the inner cavity surface. These optical surface properties deliver a framework for a quality assurance of the fabrication procedures. Furthermore, they shows promising results for a better understanding of the observed limitations in defect free cavities.

  17. Automated Surface Classification of SRF Cavities for the Investigation of the Influence of Surface Properties onto the Operational Performance

    Energy Technology Data Exchange (ETDEWEB)

    Wenskat, Marc

    2015-07-15

    Superconducting niobium radio-frequency cavities are fundamental for the European XFEL and the International Linear Collider. To use the operational advantages of superconducting cavities, the inner surface has to fulfill quite demanding requirements. The surface roughness and cleanliness improved over the last decades and with them, the achieved maximal accelerating field. Still, limitations of the maximal achieved accelerating field are observed, which are not explained by localized geometrical defects or impurities. The scope of this thesis is a better understanding of these limitations in defect free cavities based on global, rather than local, surface properties. For this goal, more than 30 cavities underwent subsequent surface treatments, cold RF tests and optical inspections within the ILC-HiGrade research program and the XFEL cavity production. An algorithm was developed which allows an automated surface characterization based on an optical inspection robot. This algorithm delivers a set of optical surface properties, which describes the inner cavity surface. These optical surface properties deliver a framework for a quality assurance of the fabrication procedures. Furthermore, they shows promising results for a better understanding of the observed limitations in defect free cavities.

  18. High-gradient near-quench-limit operation of superconducting Tesla-type cavities in scope of the International Linear Collider

    Directory of Open Access Journals (Sweden)

    Mathieu Omet

    2014-07-01

    Full Text Available We report the successful demonstration of an ILC-like high-gradient near-quench-limit operation at the Superconducting RF Test Facility at the High Energy Accelerator Research Organization (KEK in Japan. Preparation procedures necessary for the accelerator operation were conducted, such as rf phase calibration, beam-based gradient calibration, and automated beam compensation. Test runs were performed successfully for nominal operation, high-loaded Q (Q_{L} operation, and automated P_{k}Q_{L} operation. The results are described in terms of the achieved precision and stabilities of gradients and phases.

  19. High Gradient Accelerator Research

    International Nuclear Information System (INIS)

    Temkin, Richard

    2016-01-01

    The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave cold test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.

  20. High gradient RF breakdown study

    International Nuclear Information System (INIS)

    Laurent, L.; Luhmann, N.C. Jr.; Scheitrum, G.; Hanna, S.; Pearson, C.; Phillips, R.

    1998-01-01

    Stanford Linear Accelerator Center and UC Davis have been investigating high gradient RF breakdown and its effects on pulse shortening in high energy microwave devices. RF breakdown is a critical issue in the development of high power microwave sources and next generation linear accelerators since it limits the output power of microwave sources and the accelerating gradient of linacs. The motivation of this research is to find methods to increase the breakdown threshold level in X-band structures by reducing dark current. Emphasis is focused on improved materials, surface finish, and cleanliness. The test platform for this research is a traveling wave resonant ring. A 30 MW klystron is employed to provide up to 300 MW of traveling wave power in the ring to trigger breakdown in the cavity. Five TM 01 cavities have previously been tested, each with a different combination of surface polish and/or coating. The onset of breakdown was extended up to 250 MV/m with a TiN surface finish, as compared to 210 MV/m for uncoated OFE copper. Although the TiN coating was helpful in depressing the field emission, the lowest dark current was obtained with a 1 microinch surface finish, single-point diamond-turned cavity

  1. High gradient superconducting quadrupoles

    International Nuclear Information System (INIS)

    Lundy, R.A.; Brown, B.C.; Carson, J.A.; Fisk, H.E.; Hanft, R.H.; Mantsch, P.M.; McInturff, A.D.; Remsbottom, R.H.

    1987-07-01

    Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed

  2. Status and future prospects of SRF gun developments

    International Nuclear Information System (INIS)

    Teichert, Jochen

    2006-01-01

    While the concepts of DC and normal-conducting photo-injectors are well proofed, the SRF gun development still possesses a high risk. Challenges are the thermal and contaminant isolation needed between the cathode and superconducting cavity, the choice of the right photocathode and its life time, the difficulty of coupling high-average power into the gun, and beam excitation of higher order cavity modes. But in combination with SRF linacs, the SRF guns are the best solution for high current and CW operation. Thus, several R and D projects of SRF gun have been launched. The talk will give an overview of the history and progress of the SRF gun development. In more detail the technical concept, performance, and status of the Rossendorf superconducting RF gun project, a collaboration of BESSY, DESY, MBI and FZR, will be presented. (author)

  3. Superconducting rf and beam-cavity interactions

    International Nuclear Information System (INIS)

    Bisognano, J.J.

    1987-01-01

    Beam-cavity interactions can limit the beam quality and current handling capability of linear and circular accelerators. These collective effects include cumulative and regenerative transverse beam breakup (BBU) in linacs, transverse multipass beam breakup in recirculating linacs and microtrons, longitudinal and transverse coupled-bunch instabilities in storage rings, and a variety of transverse and longitudinal single-bunch phenomena (instabilities, beam breakup, and energy deposition). The superconducting radio frequency (SRF) environment has a number of features which distinguish it from room temperature configuration with regard to these beam-cavity interactions. Typically the unloaded Qs of the lower higher order modes (HOM) are at the 10 9 level and require significant damping through couplers. High gradient CW operation, which is a principal advantage of SRF, allows for better control of beam quality, which for its preservation requires added care which respect to collective phenomena. Gradients are significantly higher than those attainable with copper in CW operation but remain significantly lower than those obtainable with pulsed copper cavities. Finally, energy deposition by the beam into the cavity can occur in a cryogenic environment. In this note those characteristics of beam-cavity interactions which are of particular importance for superconducting RF cavities are highlighted. 6 refs., 4 figs

  4. SRF and RF systems for LEReC Linac

    Energy Technology Data Exchange (ETDEWEB)

    Belomestnykh, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States); Ben-Zvi, I. [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States); Brutus, J. C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fedotov, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); McIntyre, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Polizzo, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Than, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tuozzolo, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Veshcherevich, V. [Cornell Univ., Ithaca, NY (United States); Wu, Q. [Brookhaven National Lab. (BNL), Upton, NY (United States); Xiao, B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Xu, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zaltsman, A. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-05-03

    The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow rings. For the first stage of the project, LEReC-I, we will install a 704 MHz superconducting RF cavity and three normal conducting cavities operating at 9 MHz, 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.

  5. Devices for SRF material characterization

    International Nuclear Information System (INIS)

    Goudket, Philippe; Xiao, B.; Junginger, T.; Helmholtz-Zentrum Berlin

    2016-01-01

    The surface resistance Rs of superconducting materials can be obtained by measuring the quality factor of an elliptical cavity excited in a transverse magnetic mode (TM010). The value obtained has however to be taken as averaged over the whole surface. A more convenient way to obtain Rs, especially of materials which are not yet technologically ready for cavity production, is to measure small samples instead. These can be easily man ufactured at low cost, duplicated and placed in film deposition and surface analytical tools. A commonly used design for a device to measure Rs consists of a cylindrical cavity excited in a transverse electric (TE110) mode with the sample under test serving as one replaceable endplate. Such a cavity has two drawbacks. For reasonably small samples the resonant frequency will be larger than frequencies of interest concerning SRF application and it requires a reference sample of known Rs. In this article we review several devices which have been designed to overcome these limitations, reaching sub - nΩ resolution in some cases. Some of these devices also comprise a parameter space in frequency and temperature which is inaccessible to standard cavity tests, making them ideal tools to test theoretical surface resistance models.

  6. Commissioning of the 112 MHz SRF Gun and 500 MHz bunching cavities for the CeC PoP Linac

    Energy Technology Data Exchange (ETDEWEB)

    Belomestnykh, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States); Ben-Zvi, I. [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States); Brutus, J. C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Litvinenko, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States); McIntosh, P. [Science and Technology Facilities Council (STFC), Daresbury (United Kingdom). Daresbury Lab.; Moss, A. [Science and Technology Facilities Council (STFC), Daresbury (United Kingdom). Daresbury Lab.; Narayan, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Orfin, P. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pinayev, I. [Brookhaven National Lab. (BNL), Upton, NY (United States); Rao, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Skaritka, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Than, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tuozzolo, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wang, E. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wheelhouse, A. [Science and Technology Facilities Council (STFC), Daresbury (United Kingdom). Daresbury Lab.; Wu, Q. [Brookhaven National Lab. (BNL), Upton, NY (United States); Xiao, B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Xin, T. [Stony Brook Univ., NY (United States); Xu, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zaltsman, A. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-05-03

    The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase 1, a 112 MHz superconducting RF photo-emission gun and two 500 MHz normal conducting bunching cavities were installed and are under commissioning. The paper describes the Phase1 linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems

  7. SRF technology at accel for worldwide accelerator projects

    International Nuclear Information System (INIS)

    Bauer, S.; Griep, B.; Peiniger, M.; Pekeler, M.; Piel, C.; Stein, P. vom; Vogel, H.

    2003-01-01

    Within the last two years activities at ACCEL for international accelerator projects using superconducting cavities have steadily increased. We report on our production work for CERN (HOM couplers for LHC cavities), DESY (TESLA cavities and couplers), Forschungszentrum Juelich (turn key low beta SRF module), SRRC, CLS and Cornell (turn key 500 MHz SRF modules. The production a superconducting Landau accelerator module for BESSY has started recently. In addition studies are under way for a superconducting 40 MeV proton/deuteron linac and for superconducting low beta multi gap structures. (author)

  8. Modified SRF Photoinjector for the ELBE at HZDR

    CERN Document Server

    Murcek, P; Buettig, H; Michel, P; Teichert, J; Xiang, R; Kneisel, P

    2012-01-01

    The superconducting radio frequency photoinjector (SRF photoinjector) with Cs2Te cathode has been successfully operated under the collaboration of HZB, DESY, HZDR, and MBI.[1] In order to improve the gradient of the gun cavity and the beam quality, a new modified SRF gun (SRF-gun 2008) has been designed. The main updates of the new cavity design for the new photoinjector were publisched before. (ID THPPO022 on the SRF09 Berlin.) This cavity is being fabricated in Jefferson Lab. In this paper the new ideas of the further parts of the SRF-gun 2008 will be presented. The most important issue is the special design of half-cell and choke filter. The cathode cooler is also slightly changed, which simplifies the installation of the cathode cooler in the cavity. The next update is the separation of input and output of the liquid nitrogen supply, for the purpose of the stability of the nitrogen pressure as well as the better possibility of temperature measurement. Another key point is the implementation of the superco...

  9. CW SRF systems with ingot niobium and their applications

    International Nuclear Information System (INIS)

    Myneni, Ganapati

    2011-01-01

    Continuous wave (CW) superconducting radio frequency (SRF) accelerator systems are needed not only for discovery science initiatives through out the world but they are also expected to find applications in a wide variety of programs including advanced reactor cycles using thorium as nuclear fuel, commercial and university compact linacs and FEL's. However these state of the art particle accelerator systems are very expensive to build and consume significant power in their operations. In the present world economic, energy sustainability and global warming concerns, we must improve the efficiency of the CW SRF accelerator systems considerably and in a cost effective manner. In this presentation I will review the current status of the CW SRF systems including the recent advances in improving the quality factor of the SRF cavities at very much reduced costs with simplified process procedures. (author)

  10. Technology challenges for SRF guns as ERL sources in view of Rossendorf work

    International Nuclear Information System (INIS)

    Janssen, Dietmar; Buettig, Hartmut; Evtushenko, Pavel; Lehnert, Ulf; Michel, Peter; Moeller, Karsten; Murcek, Petr; Schneider, Christof; Schurig, Rico; Staufenbiel, Friedrich; Teichert, Jochen; Xiang, Rong; Stephan, Juergen; Lehmann, Wolf-Dietrich; Kamps, Thorsten; Lipka, Dirk; Volkov, Vladimir; Will, Ingo

    2006-01-01

    After successful tests of a SRF gun with a superconducting half-cell cavity a new SRF photoinjector for cw operation at the ELBE linac is under development. The paper discuss the design of the injector, the technological challenges of different components, the status of manufacturing and the expected parameters

  11. Analysis of the Cause of High External Q Modes in the JLab High Gradient Prototype Cryomodule Renascence

    Energy Technology Data Exchange (ETDEWEB)

    Li, Z.; Akcelik, V.; Xiao, L.; Lee, L.; Ng, C.; Ko, K.; /SLAC; Wang, H.; Marhauser, F.; Sekutowicz, J.; Reece, C.; Rimmer, R.; /Jefferson Lab

    2008-06-27

    The Renascence cryomodule [1] installed in CEBAF in 2007 consists of 8 cavities as shown in Figure 1. The first three cavities (No.1-No.3) in the upstream end are of the Low Loss (LL) shape design, and the remaining 5 cavities (No.4-No.8) on the beam downstream end are the High Gradient (HG) shape design. The fundamental power couplers (FPCs) are the rectangular waveguides, and the little cylindrical structures are the HOM couplers. The locations of the FPC in the last four cavities are mirrored about the beam z axis. Cavities No.4 and No.5 form a back-to-back cavity pair. Among the HG cavities installed in the Renascence cryomodule, the only identifiable difference from their fabrication documentation is that cavity No.5 received an extra EBW pass on one equator weld, specifically cell 5. The non-uniform mechanical tuning required to compensate the fundamental mode tune and flatness for the extra shrinkage of this cell is believed to contribute the most significant differences from the other HG cavities. Beam based instability studies on this cryomodule in CEBAF have shown a significant beam breakup (BBU) threshold current reduction, well below design value. Frequency spectrum peaked by the off-sided beam power indicated the cause is due to abnormal high Q modes in the cavity No.5. Measured beam off-axis position at the cavity No.5 does not correspond to the shunt impedances calculated for an ideal cavity. Low power RF measurements have identified that the problematic modes are in the second dipole band (TM110 like). Three of the modes have external Qs two orders magnitude higher than the others, while the rest of modes in the first two dipole bands are normal in terms of the design values. The cause of this abnormality and the future impact on the BBU was not able to be resolved due to the limitations of information that can be obtained from the measurements. It is important to understand the cause of this abnormality so that effective QA/QC measures can be

  12. BNL 703 MHz SRF cryomodule demonstration

    International Nuclear Information System (INIS)

    Burrill, A.; Ben-Zvi, I.; Calaga, R.; Dalesio, L.; Dottavio, T.; Gassner, D.; Hahn, H.; Hoff, L.; Kayran, D.; Kewisch, J.; Lambiase, R.; Lederle, D.; Litvinenko, V.; Mahler, G.; McIntyre, G.

    2009-01-01

    This paper will present the preliminary results of the testing of the 703 MHz SRF cryomodule designed for use in the ampere class ERL under construction at Brookhaven National Laboratory. The preliminary cavity tests, carried out at Thomas Jefferson Laboratory, demonstrated cavity performance of 20 MV/m with a Qo of 1 x 10 10 , results we expect to reproduce in the horizontal configuration. This test of the entire string assembly will allow us to evaluate all of the additional cryomodule components not previously tested in the VTA and will prepare us for our next milestone test which will be delivery of electrons from our injector through the cryomodule to the beam dump. This will also be the first demonstration of an accelerating cavity designed for use in an ampere class ERL, a key development which holds great promise for future machines

  13. Mirror-smooth surfaces and repair of defects in superconducting RF cavities by mechanical polishing

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, C. A. [Fermilab; Cooley, L. D. [Fermilab

    2012-11-22

    Mechanical techniques for polishing the inside surface of niobium superconducting radio-frequency (SRF) cavities have been systematically explored. By extending known techniques to fine polishing, mirror-like finishes were produced, with <15 nm RMS (root mean square) roughness over 1 mm2 scan area. This is an order of magnitude less than the typical roughness produced by the electropolishing of niobium cavities. The extended mechanical polishing (XMP) process was applied to several SRF cavities which exhibited equator defects that caused quench at <20 MV m-1 and were not improved by further electropolishing. Cavity optical inspection equipment verified the complete removal of these defects, and minor acid processing, which dulled the mirror finish, restored performance of the defective cells to the high gradients and quality factors measured for adjacent cells when tested with other harmonics. This innate repair feature of XMP could be used to increase manufacturing yield. Excellent superconducting properties resulted after initial process optimization, with quality factor Q of 3 × 1010 and accelerating gradient of 43 MV m-1 being attained for a single-cell TESLA cavity, which are both close to practical limits. Several repaired nine-cell cavities also attained Q > 8 × 109 at 35 MV m-1, which is the specification for the International Linear Collider. Future optimization of the process and pathways for eliminating requirements for acid processing are also discussed.

  14. Analysis list: Srf [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Srf Blood,Embryonic fibroblast,Muscle + mm9 http://dbarchive.biosciencedbc.jp/kyush...u-u/mm9/target/Srf.1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Srf.5.tsv http://dbarchive.bioscience...dbc.jp/kyushu-u/mm9/target/Srf.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Srf.Blood....tsv,http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Srf.Embryonic_fibroblast....tsv,http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Srf.Muscle.tsv http://dbarchive.biosciencedbc.jp/kyu

  15. Modified Magnicon for High-Gradient Accelerator R and D

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2011-01-01

    Analysis, and low-power cold tests are described on a modified design intended for the Ka-band pulsed magnicon now in use for high-gradient accelerator R and D and rare elementary particle searches at the Yale University Beam Physics Laboratory. The modification is mainly to the output cavity of the magnicon, which presently operates in the TM310 mode. It is proposed to substitute for this a dual-chamber TE311 cavity structure. The first chamber is to extract about 40% of the beam power (about 25 MW) at 34.272 GHz, while the second chamber is to convey the power to four WR-28 output waveguides. Minor design changes are also proposed for the penultimate 11.424 GHz cavity and the beam collector. The intention of these design changes is to allow the magnicon to operate reliably 24/7, with minor sensitivity to operating parameters.

  16. Modified Magnicon for High-Gradient Accelerator R&D

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2011-12-19

    Analysis, and low-power cold tests are described on a modified design intended for the Ka-band pulsed magnicon now in use for high-gradient accelerator R and D and rare elementary particle searches at the Yale University Beam Physics Laboratory. The modification is mainly to the output cavity of the magnicon, which presently operates in the TM310 mode. It is proposed to substitute for this a dual-chamber TE311 cavity structure. The first chamber is to extract about 40% of the beam power (about 25 MW) at 34.272 GHz, while the second chamber is to convey the power to four WR-28 output waveguides. Minor design changes are also proposed for the penultimate 11.424 GHz cavity and the beam collector. The intention of these design changes is to allow the magnicon to operate reliably 24/7, with minor sensitivity to operating parameters.

  17. The New 2nd-Generation SRF RandD Facility at Jefferson Lab: TEDF

    International Nuclear Information System (INIS)

    Reece, Charles E.; Reilly, Anthony V.

    2012-01-01

    The US Department of Energy has funded a near-complete renovation of the SRF-based accelerator research and development facilities at Jefferson Lab. The project to accomplish this, the Technical and Engineering Development Facility (TEDF) Project has completed the first of two phases. An entirely new 3,100 m 2 purpose-built SRF technical work facility has been constructed and was occupied in summer of 2012. All SRF work processes with the exception of cryogenic testing have been relocated into the new building. All cavity fabrication, processing, thermal treatment, chemistry, cleaning, and assembly work is collected conveniently into a new LEED-certified building. An innovatively designed 800 m2 cleanroom/chemroom suite provides long-term flexibility for support of multiple RandD and construction projects as well as continued process evolution. The characteristics of this first 2nd-generation SRF facility are described

  18. Relativistic klystrons for high-gradient accelerators

    International Nuclear Information System (INIS)

    Westenskow, G.A.; Aalberts, D.P.; Boyd, J.K.; Deis, G.A.; Houck, T.L.; Orzechowski, T.J.; Ryne, R.D.; Yu, S.S.; Allen, M.A.; Callin, R.S.; Deruyter, H.; Eppley, K.R.; Fant, K.S.; Fowkes, W.R.; Hoag, H.A.; Koontz, R.F.; Lavine, T.L.; Loew, G.A.; Miller, R.H.; Ruth, R.D.; Vlieks, A.E.; Wang, J.W.; Hopkins, D.B.; Sessler, A.M.; Haimson, J.; Mecklenburg, B.

    1991-01-01

    Experimental work is being performed by collaborators at LLNL, SLAC, and LBL to investigate relativistic klystrons as a possible rf power source for future high-gradient accelerators. The authors have learned how to overcome their previously reported problem of high power rf pulse shortening and have achieved peak rf power levels of 330 MW using an 11.4-GHz high-gain tube with multiple output structures. In these experiments the rf pulse is of the same duration as the beam current pulse. In addition, experiments have been performed on two short sections of a high-gradient accelerator using the rf power from a relativistic klystron. An average accelerating gradient of 84 MV/m has been achieved with 80-MW of rf power

  19. High gradient accelerators for linear light sources

    International Nuclear Information System (INIS)

    Barletta, W.A.

    1988-01-01

    Ultra-high gradient radio frequency linacs powered by relativistic klystrons appear to be able to provide compact sources of radiation at XUV and soft x-ray wavelengths with a duration of 1 picosecond or less. This paper provides a tutorial review of the physics applicable to scaling the present experience of the accelerator community to the regime applicable to compact linear light sources. 22 refs., 11 figs., 21 tabs

  20. Prototyping high-gradient mm-wave accelerating structures

    International Nuclear Information System (INIS)

    Nanni, Emilio A.; Dolgashev, Valery A.; Haase, Andrew; Neilson, Jeffrey; Tantawi, Sami

    2017-01-01

    We present single-cell accelerating structures designed for high-gradient testing at 110 GHz. The purpose of this work is to study the basic physics of ultrahigh vacuum RF breakdown in high-gradient RF accelerators. The accelerating structures are π-mode standing-wave cavities fed with a TM 01 circular waveguide. The structures are fabricated using precision milling out of two metal blocks, and the blocks are joined with diffusion bonding and brazing. The impact of fabrication and joining techniques on the cell geometry and RF performance will be discussed. First prototypes had a measured Q 0 of 2800, approaching the theoretical design value of 3300. The geometry of these accelerating structures are as close as practical to singlecell standing-wave X-band accelerating structures more than 40 of which were tested at SLAC. This wealth of X-band data will serve as a baseline for these 110 GHz tests. Furthermore, the structures will be powered with short pulses from a MW gyrotron oscillator. RF power of 1 MW may allow an accelerating gradient of 400 MeV/m to be reached.

  1. Plasma ignition and tuning in different cells of a 1.3 GHz nine-cell superconducting radio frequency cavity: Proof of principle

    Science.gov (United States)

    Tyagi, P. V.; Moss, Andrew; Goudket, Philippe; Pattalwar, Shrikant; Herbert, Joe; Valizadeh, Reza; McIntosh, Peter

    2018-06-01

    Field emission is one of the critical issues in the superconducting radio frequency (SRF) cavities and can degrade their accelerating gradient during operation. The contamination present at top surface of the SRF cavity is one of the foremost reasons for field emission. Plasma based surface processing can be a viable option to eliminate such surface contaminants and enhance performance of the SRF cavity especially for in-situ applications. These days, 1.3 GHz nine-cell SRF cavity has become baseline standard for many particle accelerators, it is of interest to develop plasma cleaning technique for such SRF cavities. In the development of the plasma processing technique for SRF cavities, the most challenging task is to ignite and tune the plasma in different cells of the SRF cavity. At Daresbury laboratory, UK, we have successfully achieved plasma ignition in different cells of a 1.3 GHz nine-cell SRF cavity. The plasma ignition in different cells of the cavity was accomplished at room temperature towards room temperature plasma cleaning of the SRF cavity surface. Here, we report the successful demonstration of the plasma ignition in different cells of a 1.3 GHz nine-cell SRF cavity.

  2. State of the art of multicell SC cavities and perspectives

    International Nuclear Information System (INIS)

    Peter Kneisel

    2002-01-01

    Superconducting cavity technology has made major progresses in the last decade with the introduction of high purity niobium on an industrial scale and, at the same time, by an improved understanding of the limiting processes in cavity performance, such as multipacting, field emission loading and thermal break-down. Multicell niobium cavities for beta = 1 particle acceleration, e.g. for the TESLA project, are routinely exceeding gradients of Eacc = 20 MV/m after the application of surface preparation techniques such as buffered chemical polishing or electropolishing, high pressure ultrapure water rinsing, UHV heat treatment and clean room assembly. The successes of the technology for beta = 1 accelerators has triggered a whole set of possible future applications for beta < 1 particle acceleration such as spallation neutron sources (SNS, ESS), transmutation of nuclear waste (TRASCO, ASH) or rare isotopes (RIA). The most advanced of these projects is SNS now under construction at Oak Ridge National Laboratory. This paper will review the technical solutions adopted to advance SRF technology and their impact on cavity performance, based on the SNS prototyping efforts. 2K at these high gradients are no longer out of reach. For the accelerator builder the challenge remains to come up with a good and reasonable design, which takes into account the status of the technology and does not over-estimate the achievable cavity performances in a large assembly such as, e.g., a multi-cavity cryo-module. In the following the criteria for multi-cell sc cavity design are reviewed and it is attempted to give a snapshot of the present status of multi-cell cavity performances

  3. Impact of cool-down conditions at T_{c} on the superconducting rf cavity quality factor

    Directory of Open Access Journals (Sweden)

    J.-M. Vogt

    2013-10-01

    Full Text Available Many next-generation, high-gradient accelerator applications, from energy-recovery linacs to accelerator-driven systems (ADS rely on continuous wave (CW operation for which superconducting radio-frequency (SRF systems are the enabling technology. However, while SRF cavities dissipate little power, they must be cooled by liquid helium and for many CW accelerators the complexity as well as the investment and operating costs of the cryoplant can prove to be prohibitive. We investigated ways to reduce the dynamic losses by improving the residual resistance (R_{res} of niobium cavities. Both the material treatment and the magnetic shielding are known to have an impact. In addition, we found that R_{res} can be reduced significantly when the cool-down conditions during the superconducting phase transition of the niobium are optimized. We believe that not only do the cool-down conditions impact the level to which external magnetic flux is trapped in the cavity but also that thermoelectric currents are generated which in turn create additional flux that can be trapped. Therefore, we investigated the generation of flux and the dynamics of flux trapping and release in a simple model niobium-titanium system that mimics an SRF cavity in its helium tank. We indeed found that thermal gradients along the system during the superconducting transition can generate a thermoelectric current and magnetic flux, which subsequently can be trapped. These effects may explain the observed variation of the cavity’s R_{res} with cool-down conditions.

  4. Relativistic klystron research for high gradient accelerators

    International Nuclear Information System (INIS)

    Allen, M.A.; Callin, R.S.; Deruyter, H.

    1988-06-01

    Relativistic klystrons are being developed as a power source for high gradient accelerator applications which include large linear electron--positron colliders, compact accelerators, and FEL sources. We have attained 200MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here on the design of our first klystrons, the results of our experiments so far, and some of our plans for the near future. 5 refs., 7 figs

  5. Easing Gently into OpenSRF, Part 2

    OpenAIRE

    Dan Scott

    2010-01-01

    The Open Service Request Framework (or OpenSRF, pronounced "open surf") is an inter-application message passing architecture built on XMPP (aka "jabber"). The Evergreen open source library system is built on an OpenSRF architecture to support loosely coupled individual components communicating over an OpenSRF messaging bus. This article introduces OpenSRF, demonstrates how to build OpenSRF services through simple code examples, explains the technical foundations on which OpenSRF is built, and...

  6. Easing Gently into OpenSRF, Part 1

    OpenAIRE

    Dan Scott

    2010-01-01

    The Open Service Request Framework (or OpenSRF, pronounced "open surf") is an inter-application message passing architecture built on XMPP (aka "jabber"). The Evergreen open source library system is built on an OpenSRF architecture to support loosely coupled individual components communicating over an OpenSRF messaging bus. This article introduces OpenSRF, demonstrates how to build OpenSRF services through simple code examples, explains the technical foundations on which OpenSRF is built, and...

  7. How to Achieve the Best SRF Performance: (Practical) Limitations and Possible Solutions

    International Nuclear Information System (INIS)

    Antoine, Claire Z

    2014-01-01

    This chapter presents in the first part the requirement for the surface preparation of RF Niobium cavities and its justification in term s of physical origin of limitation (e.g. cleanliness and field emission, influence of the surface treatments, morphology and surface damage, etc.). In the second part we discuss the different models describing the ultimate limits of SRF cavities, and we present one of the possible ways to overcome Niobium monopoly toward higher performances

  8. How to Achieve the Best SRF Performance: (Practical) Limitations and Possible Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Antoine, Claire Z [IRFU, Saclay (France)

    2014-07-01

    This chapter presents in the first part the requirement for the surface preparation of RF Niobium cavities and its justification in term s of physical origin of limitation (e.g. cleanliness and field emission, influence of the surface treatments, morphology and surface damage, etc.). In the second part we discuss the different models describing the ultimate limits of SRF cavities, and we present one of the possible ways to overcome Niobium monopoly toward higher performances.

  9. High gradient lens for charged particle beam

    Science.gov (United States)

    Chen, Yu-Jiuan

    2014-04-29

    Methods and devices enable shaping of a charged particle beam. A dynamically adjustable electric lens includes a series of alternating a series of alternating layers of insulators and conductors with a hollow center. The series of alternating layers when stacked together form a high gradient insulator (HGI) tube to allow propagation of the charged particle beam through the hollow center of the HGI tube. A plurality of transmission lines are connected to a plurality of sections of the HGI tube, and one or more voltage sources are provided to supply an adjustable voltage value to each transmission line of the plurality of transmission lines. By changing the voltage values supplied to each section of the HGI tube, any desired electric field can be established across the HGI tube. This way various functionalities including focusing, defocusing, acceleration, deceleration, intensity modulation and others can be effectuated on a time varying basis.

  10. Coreless Concept for High Gradient Induction Cell

    International Nuclear Information System (INIS)

    Krasnykh, Anatoly

    2008-01-01

    An induction linac cell for a high gradient is discussed. The proposed solid state coreless approach for the induction linac topology (SLIM(reg s ign)) is based on nanosecond mode operation. This mode may have an acceleration gradient comparable with gradients of rf- accelerator structures. The discussed induction system has the high electric efficiency. The key elements are a solid state semiconductor switch and a high electric density dielectric with a thin section length. The energy in the induction system is storied in the magnetic field. The nanosecond current break-up produces the high voltage. The induced voltage is used for acceleration. This manner of an operation allows the use of low voltage elements in the booster part and achieves a high accelerating gradient. The proposed topology was tested in POP (proof of principle) experiments

  11. 1.3 GHz superconducting RF cavity program at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Ginsburg, C.M.; Arkan, T.; Barbanotti, S.; Carter, H.; Champion, M.; Cooley, L.; Cooper, C.; Foley, M.; Ge, M.; Grimm, C.; Harms, E.; /Fermilab

    2011-03-01

    At Fermilab, 9-cell 1.3 GHz superconducting RF (SRF) cavities are prepared, qualified, and assembled into cryomodules (CMs) for Project X, an International Linear Collider (ILC), or other future projects. The 1.3 GHz SRF cavity program includes targeted R&D on 1-cell 1.3 GHz cavities for cavity performance improvement. Production cavity qualification includes cavity inspection, surface processing, clean assembly, and one or more cryogenic low-power CW qualification tests which typically include performance diagnostics. Qualified cavities are welded into helium vessels and are cryogenically tested with pulsed high-power. Well performing cavities are assembled into cryomodules for pulsed high-power testing in a cryomodule test facility, and possible installation into a beamline. The overall goals of the 1.3 GHz SRF cavity program, supporting facilities, and accomplishments are described.

  12. SRF Performance of CEBAF After Thermal Cycle to Ambient Temperature

    International Nuclear Information System (INIS)

    Robert Rimmer; Jay Benesch; Joseph Preble; Charles Reece

    2005-01-01

    In September 2003, in the wake of Hurricane Isabel, JLab was without power for four days after a tree fell on the main power lines feeding the site. This was long enough to lose insulating vacuum in the cryomodules and cryogenic systems resulting in the whole accelerator warming up and the total loss of the liquid helium inventory. This thermal cycle stressed many of the cryomodule components causing several cavities to become inoperable due to helium to vacuum leaks. At the same time the thermal cycle released years of adsorbed gas from the cold surfaces. Over the next days and weeks this gas was pumped away, the insulating vacuum was restored and the machine was cooled back down and re-commissioned. In a testament to the robustness of SRF technology, only a small loss in energy capability was apparent, although individual cavities had quite different field-emission characteristics compared to before the event. In Summer 2004 a section of the machine was again cycled to room temperature during the long maintenance shutdown. We report on the overall SRF performance of the machine after these major disturbances and on efforts to characterize and optimize the new behavior for high-energy running

  13. Fast thermometry for superconducting rf cavity testing

    International Nuclear Information System (INIS)

    Orris, Darryl; Bellantoni, Leo; Carcagno, Ruben H.; Edwards, Helen; Harms, Elvin Robert; Khabiboulline, Timergali N.; Kotelnikov, Sergey; Makulski, Andrzej; Nehring, Roger; Pischalnikov, Yuriy; Fermilab

    2007-01-01

    Fast readout of strategically placed low heat capacity thermometry can provide valuable information of Superconducting RF (SRF) cavity performance. Such a system has proven very effective for the development and testing of new cavity designs. Recently, several resistance temperature detectors (RTDs) were installed in key regions of interest on a new 9 cell 3.9 GHz SRF cavity with integrated HOM design at FNAL. A data acquisition system was developed to read out these sensors with enough time and temperature resolution to measure temperature changes on the cavity due to heat generated from multipacting or quenching within power pulses. The design and performance of the fast thermometry system will be discussed along with results from tests of the 9 cell 3.9GHz SRF cavity

  14. Fast thermometry for superconducting rf cavity testing

    Energy Technology Data Exchange (ETDEWEB)

    Orris, Darryl; Bellantoni, Leo; Carcagno, Ruben H.; Edwards, Helen; Harms, Elvin Robert; Khabiboulline, Timergali N.; Kotelnikov, Sergey; Makulski, Andrzej; Nehring, Roger; Pischalnikov, Yuriy; /Fermilab

    2007-06-01

    Fast readout of strategically placed low heat capacity thermometry can provide valuable information of Superconducting RF (SRF) cavity performance. Such a system has proven very effective for the development and testing of new cavity designs. Recently, several resistance temperature detectors (RTDs) were installed in key regions of interest on a new 9 cell 3.9 GHz SRF cavity with integrated HOM design at FNAL. A data acquisition system was developed to read out these sensors with enough time and temperature resolution to measure temperature changes on the cavity due to heat generated from multipacting or quenching within power pulses. The design and performance of the fast thermometry system will be discussed along with results from tests of the 9 cell 3.9GHz SRF cavity.

  15. Operational optimization of large-scale SRF accelerators

    International Nuclear Information System (INIS)

    J. R. Delayen; L. R. Doolittle; C. E. Reece

    1999-01-01

    Unlike other types of accelerator subsystems, because of the flexibility in setting the gradient in each cavity, an SRF linac has many operational degrees of freedom. The overall linac has an operational envelope (beam voltage and current) that depends on acceptable reliability, cryogenic capacity, and RF power budget. For economic and end-user physics reasons, one typically wants to run as close to the edge of the operational envelope as possible. With about 160 cavities in each of the CEBAF linacs. The authors have been forced to treat this problem in a very general way, and satisfy other non-fundamental needs as energy lock and rapid recovery from failures. They present a description of the relevant diverse constraints and the solution developed for CEBAF

  16. Variable high gradient permanent magnet quadrupole (QUAPEVA)

    Science.gov (United States)

    Marteau, F.; Ghaith, A.; N'Gotta, P.; Benabderrahmane, C.; Valléau, M.; Kitegi, C.; Loulergue, A.; Vétéran, J.; Sebdaoui, M.; André, T.; Le Bec, G.; Chavanne, J.; Vallerand, C.; Oumbarek, D.; Cosson, O.; Forest, F.; Jivkov, P.; Lancelot, J. L.; Couprie, M. E.

    2017-12-01

    Different applications such as laser plasma acceleration, colliders, and diffraction limited light sources require high gradient quadrupoles, with strength that can reach up to 200 T/m for a typical 10 mm bore diameter. We present here a permanent magnet based quadrupole (so-called QUAPEVA) composed of a Halbach ring and surrounded by four permanent magnet cylinders. Its design including magnetic simulation modeling enabling us to reach 201 T/m with a gradient variability of 45% and mechanical issues are reported. Magnetic measurements of seven systems of different lengths are presented and confirmed the theoretical expectations. The variation of the magnetic center while changing the gradient strength is ±10 μm. A triplet of QUAPEVA magnets is used to efficiently focus a beam with large energy spread and high divergence that is generated by a Laser Plasma Acceleration source for a free electron laser demonstration and has enabled us to perform beam based alignment and control the dispersion of the beam.

  17. Asymmetric Uncertainty Expression for High Gradient Aerodynamics

    Science.gov (United States)

    Pinier, Jeremy T

    2012-01-01

    When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.

  18. SRF Clean Rooms and Cryomodule Assembly

    Data.gov (United States)

    Federal Laboratory Consortium — Three primary cleanroom facilities used for the SRF cryomodule production program are available. All 3 clean rooms have class 10 and class 100 areas. The largest is...

  19. High-gradient compact linear accelerator

    Science.gov (United States)

    Carder, Bruce M.

    1998-01-01

    A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter.

  20. Tuner Design for PEFP Superconducting RF Cavities

    International Nuclear Information System (INIS)

    Tang, Yazhe; An, Sun; Zhang, Liping; Cho, Yong Sub

    2009-01-01

    A superconducting radio frequency (SRF) cavity will be used to accelerate a proton beam after 100 MeV at 700 MHz in a linac of the Proton Engineering Frontier Project (PEFP) and its extended project. In order to control the SRF cavity's operating frequency at a low temperature, a new tuner has been developed for the PEFP SRF cavities. Each PEFP superconducting RF cavity has one tuner to match the cavity resonance frequency with the desired accelerator operating frequency; or to detune a cavity frequency a few bandwidths away from a resonance, so that the beam will not excite the fundamental mode, when the cavity is not being used for an acceleration. The PEFP cavity tuning is achieved by varying the total length of the cavity. The length of the cavity is controlled differentially by tuner acting with respect to the cavity body. The PEFP tuner is attached to the helium vessel and drives the cavity Field Probe (FP) side to change the frequency of the cavity

  1. R&D progress in SRF surface preparation with centrifugal barrel polishing (cbp) for both Nb and Cu

    Energy Technology Data Exchange (ETDEWEB)

    Palczewski, Ari [JLAB

    2013-09-01

    Centrifugal Barrel polishing (CBP) is becoming a common R&D tool for SRF cavity preparation around the world. During the CBP process a cylindrically symmetric SRF cavity is filled with relatively cheap and environmentally friendly abrasive and sealed. The cavity is then spun around a cylindrically symmetric axis at high speeds uniformly conditioning the inner surface. This uniformity is especially relevant for SRF application because many times a single manufacturing defects limits cavity?s performance well below it?s theoretical limit. In addition CBP has created surfaces with roughness?s on the order of 10?s of nm which create a unique surface for wet chemistry or thin film deposition. CBP is now being utilized at Jefferson Laboratory, Fermi Laboratory and Cornell University in the US, Deutsches Elektronen-Synchrotron in Germany, Laboratori Nazionali di Legnaro in Italy, and Raja Ramanna Centre for Advanced Technology in India. In this talk we will present current CBP research from each lab including equipment, baseline recipes, cavity removal rates and subsequent cryogenic cavity tests on niobium as well as copper cavities where available.

  2. Study of RF flux penetration on Nb for SRF Applications

    Science.gov (United States)

    Oripov, Bakhrom; Anlage, Steven

    Superconducting Radio Frequency (SRF) cavities are being widely used in new generation particle accelerators. Based on the needs of the SRF community to identify defects on Nb surfaces, a novel near-field magnetic field microwave microscope was successfully built using a magnetic writer from a conventional perpendicular magnetic recording hard-disk drive. Using our probe, we performed microwave measurement of both third P3f\\ (Pf,T) and fifth P5f (Pf,T) harmonic responses and its dependence on temperature and rf input power by applying a strong and localized RF magnetic field on high quality Nb films. Our preliminary results show significant difference in low-field and high-field harmonic responses. Above a temperature-dependent onset field H1 periodic structures in the harmonic response vs rf field amplitude data emerges. Similar behavior is observed in both bulk Nb and thin film Nb samples. We attribute this periodic response to vortex nonlinearity. Using our microscope, we are able to measure a local lower critical field for vortex formation Hc,v (in arbitrary units), and compare the Hc,v's of samples produced with different techniques and chemical treatments. This work is funded by US Department of Energy through Grant # DE-SC0012036T and CNAM.

  3. Development of a high gradient rf system using a nanocrystalline soft magnetic alloy

    Directory of Open Access Journals (Sweden)

    Chihiro Ohmori

    2013-11-01

    Full Text Available The future high intensity upgrade project of the J-PARC (Japan Proton Accelerator Research Complex MR (Main Ring includes developments of high gradient rf cavities and magnet power supplies for high repetition rate. The scenario describing the cavity replacements is reported. By the replacement plan, the total acceleration voltage will be almost doubled, while the number of rf stations remains the same. The key issue is the development of a high gradient rf system using high impedance magnetic alloy, FT3L. The FT3L is produced by the transverse magnetic field annealing although the present cavity for the J-PARC adopts the magnetic alloy, FT3M, which is annealed without magnetic field. After the test production using a large spectrometer magnet in 2011, a dedicated production system for the FT3L cores was assembled in 2012. This setup demonstrated that we can produce material with 2 times higher μ_{p}^{′}Qf product compared to the cores used for present cavities. In this summer, the production system was moved to the company from J-PARC and is used for mass production of 280 FT3L cores for the J-PARC MR. The cores produced in the first test production are already used for standard machine operation. The operation experience shows that the power loss in the cores was reduced significantly as expected.

  4. NB Coating Developments with HIPIMS for SRF Applications

    CERN Document Server

    Terenziani, G; Junginger, T; Santillana, I A; Ehiasarian, A P

    2013-01-01

    In the last few years the interest of the thin film science and technology community on High Impulse Power Magnetron Sputtering (HIPIMS) coatings has steadily increased. HIPIMS literature shows that better thin film morphology, denser and smoother films can be achieved when compared with standard dc Magnetron Sputtering (dcMS) coating technology [1]. Furthermore the capability of HIPIMS to produce a high quantity of ionized species [2,3] can allow conformal coatings also for complex geometries. A study is under way at CERN to apply this technology for the Nb coating of SRF 1.3-1.5 GHz Cu cavities, and in parallel at SHU the plasma physics and its correlation with film morphology are being investigated [2]. Recent results achieved with this technique are presented in the paper.

  5. HG2006 Workshop on High-Gradient Radio Frequency

    CERN Multimedia

    2006-01-01

    Meeting to be held at CERN on 25-27 September 2006 in Room 40/S2-B01 (Building 40). The objective of the workshop is to bring the high-gradient RF community together to present and discuss recent theoretical and experimental developments. Significant progress has recently been made in understanding the basic physics of rf breakdown and developing techniques for achieving higher gradients. This workshop should contribute to maintaining these efforts and to promoting contacts and collaboration. The scientific programme will be organized in half day sessions dedicated to: High-gradient rf experimental results Theory and computation High-gradient technology, materials and processing Specialized experiments on related high-gradient or high-power phenomenon like dc discharge and pulsed surface heating Reports from collaborations and projects. Each session will consist of selected presentations followed by a dedicated discussion. Information about the meeting and participant registration is available at http...

  6. Defect Detection in Superconducting Radiofrequency Cavity Surface Using C + + and OpenCV

    Science.gov (United States)

    Oswald, Samantha; Thomas Jefferson National Accelerator Facility Collaboration

    2014-03-01

    Thomas Jefferson National Accelerator Facility (TJNAF) uses superconducting radiofrequency (SRF) cavities to accelerate an electron beam. If theses cavities have a small particle or defect, it can degrade the performance of the cavity. The problem at hand is inspecting the cavity for defects, little bubbles of niobium on the surface of the cavity. Thousands of pictures have to be taken of a single cavity and then looked through to see how many defects were found. A C + + program with Open Source Computer Vision (OpenCV) was constructed to reduce the number of hours searching through the images and finds all the defects. Using this code, the SRF group is now able to use the code to identify defects in on-going tests of SRF cavities. Real time detection is the next step so that instead of taking pictures when looking at the cavity, the camera will detect all the defects.

  7. SRF Performance of CEBAF After Thermal Cycle to Ambient Temperature

    CERN Document Server

    Rimmer, Robert; Preble, Joseph P; Reece, Charles E

    2005-01-01

    In September 2003, in the wake of Hurricane Isabel, JLab was without power for four days after a tree fell on the main power lines feeding the site. This was long enough to lose insulating vacuum in the cryomodules and cryogenic systems resulting in the whole accelerator warming up and the total loss of the liquid helium inventory. This thermal cycle stressed many of the cryomodule components causing several cavities to become inoperable due to helium to vacuum leaks. At the same time the thermal cycle released years of adsorbed gas from the cold surfaces. Over the next days and weeks this gas was pumped away, the insulating vacuum was restored and the machine was cooled back down and re-commissioned. In a testament to the robustness of SRF technology, only a small loss in energy capability was apparent, although individual cavities had quite different field-emission characteristics compared to before the event. In Summer 2004 a section of the machine was again cycled to room temperature during the long maint...

  8. Analysis Of Post-Wet-Chemistry Heat Treatment Effects On Nb SRF Surface Resistance

    International Nuclear Information System (INIS)

    Dhakal, Pashupati; Ciovati, Gianluigi; Kneisel, Peter K.; Myneni, Ganapati Rao

    2014-01-01

    Most of the current research in superconducting radio frequency (SRF) cavities is focused on ways to reduce the construction and operating cost of SRF-based accelerators as well as on the development of new or improved cavity processing techniques. The increase in quality factors is the result of the reduction of the surface resistance of the materials. A recent test on a 1.5 GHz single cell cavity made from ingot niobium of medium purity and heat treated at 1400 °C in a ultra-high vacuum induction furnace resulted in a residual resistance of ∼ 1nΩ and a quality factor at 2.0 K increasing with field up to ∼ 5A-10 10 at a peak magnetic field of 90 mT. In this contribution, we present some results on the investigation of the origin of the extended Q 0 -increase, obtained by multiple HF rinses, oxypolishing and heat treatment of A ''all NbA'' cavities

  9. Microscopic Investigation of Materials Limitations of Superconducting RF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Anlage, Steven [Univ. of Maryland, College Park, MD (United States)

    2017-08-04

    Our overall goal is to contribute to the understanding of defects that limit the high accelerating gradient performance of Nb SRF cavities. Our approach is to develop a microscopic connection between materials defects and SRF performance. We developed a near-field microwave microscope to establish this connection. The microscope is based on magnetic hard drive write heads, which are designed to create very strong rf magnetic fields in very small volumes on a surface.

  10. Adaptive compensation of Lorentz force detuning in superconducting RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Pischalnikov, Yuriy [Fermilab; Schappert, Warren [Fermilab

    2011-11-01

    The Lorentz force can dynamically detune pulsed Superconducting RF cavities and considerable additional RF power can be required to maintain the accelerating gradient if no effort is made to compensate. Fermilab has developed an adaptive compensation system for cavities in the Horizontal Test Stand, in the SRF Accelerator Test Facility, and for the proposed Project X.

  11. Advances in high-gradient magnetic fishing for bioprocessing

    DEFF Research Database (Denmark)

    Goncalves Gomes, Claudia Sofia

    2006-01-01

    High-gradient magnetic fishing” (HGMF) er en metode til processering af fødestrømme med biologiske molekyler. HGMF integrerer brugen af superparamagnetiske adsorbenter med separation og processering med høj-gradient magnetisk separation (HGMS) i et magnetisk filter. Adsorbenterne er uporøse og...

  12. Near-Field Microwave Magnetic Nanoscopy of Superconducting Radio Frequency Cavity Materials

    OpenAIRE

    Tai, Tamin; Ghamsari, Behnood G.; Bieler, Thomas R.; Tan, Teng; Xi, X. X.; Anlage, Steven M.

    2013-01-01

    A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two new measurements are performed to demonstrate these capabilities with a novel near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high Residual- Resistance-Ratio bulk Nb sample showing strong localized nonlinear response for the first time, with surfa...

  13. Flux pinning characteristics in cylindrical ingot niobium used in superconducting radio frequency cavity fabrication

    OpenAIRE

    Dhavale, Asavari S.; Dhakal, Pashupati; Polyanskii, Anatolii A.; Ciovati, Gianluigi

    2012-01-01

    We present the results of from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low temperature baking as they are typically applied to SRF cavities. The magnetization data were fitted using a modified critical state model. The critical current density Jc and pinning force Fp are calculat...

  14. Dielectric-Lined High-Gradient Accelerator Structure

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2012-04-24

    Rectangular particle accelerator structures with internal planar dielectric elements have been studied, with a view towards devising structures with lower surface fields for a given accelerating field, as compared with structures without dielectrics. Success with this concept is expected to allow operation at higher accelerating gradients than otherwise on account of reduced breakdown probabilities. The project involves studies of RF breakdown on amorphous dielectrics in test cavities that could enable high-gradient structures to be built for a future multi-TeV collider. The aim is to determine what the limits are for RF fields at the surfaces of selected dielectrics, and the resulting acceleration gradient that could be achieved in a working structure. The dielectric of principal interest in this study is artificial CVD diamond, on account of its advertised high breakdown field ({approx}2 GV/m for dc), low loss tangent, and high thermal conductivity. Experimental studies at mm-wavelengths on materials and structures for achieving high acceleration gradient were based on the availability of the 34.3 GHz third-harmonic magnicon amplifier developed by Omega-P, and installed at the Yale University Beam Physics Laboratory. Peak power from the magnicon was measured to be about 20 MW in 0.5 {micro}s pulses, with a gain of 54 dB. Experiments for studying RF high-field effects on CVD diamond samples failed to show any evidence after more than 10{sup 5} RF pulses of RF breakdown up to a tangential surface field strength of 153 MV/m; studies at higher fields were not possible due to a degradation in magnicon performance. A rebuild of the tube is underway at this writing. Computed performance for a dielectric-loaded rectangular accelerator structure (DLA) shows highly competitive properties, as compared with an existing all-metal structure. For example, comparisons were made of a DLA structure having two planar CVD diamond elements with a all-metal CERN structure HDS

  15. Dielectric-Lined High-Gradient Accelerator Structure

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2012-01-01

    Rectangular particle accelerator structures with internal planar dielectric elements have been studied, with a view towards devising structures with lower surface fields for a given accelerating field, as compared with structures without dielectrics. Success with this concept is expected to allow operation at higher accelerating gradients than otherwise on account of reduced breakdown probabilities. The project involves studies of RF breakdown on amorphous dielectrics in test cavities that could enable high-gradient structures to be built for a future multi-TeV collider. The aim is to determine what the limits are for RF fields at the surfaces of selected dielectrics, and the resulting acceleration gradient that could be achieved in a working structure. The dielectric of principal interest in this study is artificial CVD diamond, on account of its advertised high breakdown field (∼2 GV/m for dc), low loss tangent, and high thermal conductivity. Experimental studies at mm-wavelengths on materials and structures for achieving high acceleration gradient were based on the availability of the 34.3 GHz third-harmonic magnicon amplifier developed by Omega-P, and installed at the Yale University Beam Physics Laboratory. Peak power from the magnicon was measured to be about 20 MW in 0.5 (micro)s pulses, with a gain of 54 dB. Experiments for studying RF high-field effects on CVD diamond samples failed to show any evidence after more than 10 5 RF pulses of RF breakdown up to a tangential surface field strength of 153 MV/m; studies at higher fields were not possible due to a degradation in magnicon performance. A rebuild of the tube is underway at this writing. Computed performance for a dielectric-loaded rectangular accelerator structure (DLA) shows highly competitive properties, as compared with an existing all-metal structure. For example, comparisons were made of a DLA structure having two planar CVD diamond elements with a all-metal CERN structure HDS operating at 30

  16. Linear beam dynamics and ampere class superconducting RF cavities at RHIC

    Science.gov (United States)

    Calaga, Rama R.

    The Relativistic Heavy Ion Collider (RHIC) is a hadron collider designed to collide a range of ions from protons to gold. RHIC operations began in 2000 and has successfully completed five physics runs with several species including gold, deuteron, copper, and polarized protons. Linear optics and coupling are fundamental issues affecting the collider performance. Measurement and correction of optics and coupling are important to maximize the luminosity and sustain stable operation. A numerical approach, first developed at SLAC, was implemented to measure linear optics from coherent betatron oscillations generated by ac dipoles and recorded at multiple beam position monitors (BPMs) distributed around the collider. The approach is extended to a fully coupled 2D case and equivalence relationships between Hamiltonian and matrix formalisms are derived. Detailed measurements of the transverse coupling terms are carried out at RHIC and correction strategies are applied to compensate coupling both locally and globally. A statistical approach to determine BPM reliability and performance over the past three runs and future improvements also discussed. Aiming at a ten-fold increase in the average heavy-ion luminosity, electron cooling is the enabling technology for the next luminosity upgrade (RHIC II). Cooling gold ion beams at 100 GeV/nucleon requires an electron beam of approximately 54 MeV and a high average current in the range of 50-200 mA. All existing e-Coolers are based on low energy DC accelerators. The only viable option to generate high current, high energy, low emittance CW electron beam is through a superconducting energy-recovery linac (SC-ERL). In this option, an electron beam from a superconducting injector gun is accelerated using a high gradient (˜ 20 MV/m) superconducting RF (SRF) cavity. The electrons are returned back to the cavity with a 180° phase shift to recover the energy back into the cavity before being dumped. A design and development of a half

  17. Simulation Study Using an Injection Phase-locked Magnetron as an Alternative Source for SRF Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haipeng [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Plawski, Tomasz E. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Rimmer, Robert A. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2015-09-01

    As a drop-in replacement for the CEBAF CW klystron system, a 1497 MHz, CW-type high-efficiency magnetron using injection phase lock and amplitude variation is attractive. Amplitude control using magnetic field trimming and anode voltage modulation has been studied using analytical models and MATLAB/Simulink simulations. Since the 1497 MHz magnetron has not been built yet, previously measured characteristics of a 2.45GHz cooker magnetron are used as reference. The results of linear responses to the amplitude and phase control of a superconducting RF (SRF) cavity, and the expected overall benefit for the current CEBAF and future MEIC RF systems are presented in this paper.

  18. High Gradient Accelerating Structures for Carbon Therapy Linac

    Energy Technology Data Exchange (ETDEWEB)

    Kutsaev, Sergey; Agustsson, R.; Faillace, L.; Goel, A.; Mustapha, B.; Nassiri, A.; Ostroumov, P.; Plastun, A.; Savin, E.

    2016-05-01

    Carbon therapy is the most promising among techniques for cancer treatment, as it has demonstrated significant improvements in clinical efficiency and reduced toxicity profiles in multiple types of cancer through much better localization of dose to the tumor volume. RadiaBeam, in collaboration with Argonne National Laboratory, are developing an ultra-high gradient linear accelerator, Advanced Compact Carbon Ion Linac (ACCIL), for the delivery of ion-beams with end-energies up to 450 MeV/u for 12C6+ ions and 250 MeV for protons. In this paper, we present a thorough comparison of standing and travelling wave designs for high gradient S-Band accelerating structures operating with ions at varying velocities, relative to the speed of light, in the range 0.3-0.7. In this paper we will compare these types of accelerating structures in terms of RF, beam dynamics and thermo-mechanical performance.

  19. Experimental and theoretical investigation of high gradient acceleration

    International Nuclear Information System (INIS)

    Wurtele, J.S.; Bekefi, G.; Chen, C.; Chen, S.C.; Temkin, R.J.

    1993-01-01

    This report contains a technical progress summary of the research conducted under the auspices of DOE Grant No. DE-AC02-91-ER40648, ''Experimental and Theoretical Investigations of High Gradient Acceleration''. This grant supports three research tasks: Task A consists of the design, fabrication and testing of a 17GHz RF photocathode gun, which can produce 2ps electron pulses with up to 1nC of charge at 2MeV energy and at a 1OHz repetition rate. Task B supports the testing of high gradient acceleration at 33GHz structure, and Task C comprises theoretical investigations, both in support of the experimental tasks and on critical physics issues for the development of high energy linear colliders

  20. High-gradient electron accelerator powered by a relativisitic klystron

    International Nuclear Information System (INIS)

    Allen, M.A.; Boyd, J.K.; Callin, R.S.; Deruyter, H.; Eppley, K.R.; Fant, K.S.; Fowkes, W.R.; Haimson, J.; Hoag, H.A.; Hopkins, D.B.; Houck, T.; Koontz, R.F.; Lavine, T.L.; Loew, G.A.; Mecklenburg, B.; Miller, R.H.; Ruth, R.D.; Ryne, R.D.; Sessler, A.M.; Vlieks, A.E.; Wang, J.W.; Westenskow, G.A.; Yu, S.S.

    1989-01-01

    We have used relativistic klystron technology to extract 290 MW of peak power at 11.4 GHz from an induction linac beam, and to power a short 11.4-GHz high-gradient accelerator. We have measured rf phase stability, field emission, and the momentum spectrum of an accelerated electron beam. An average accelerating gradient of 84 MV/m has been achieved with 80 MW of relativistic klystron power

  1. A linear accelerator power amplification system for high gradient structure research

    International Nuclear Information System (INIS)

    Haimson, J.; Mecklenburg, B.

    1999-01-01

    The ongoing development of linear collider high power RF sources and pulse compression systems has resulted in substantial progress towards a goal of providing a peak RF power level of approximately 250 MW at the input of the accelerator structure. While the immediate development and the high power testing of specialized waveguide components required for power transmission at these high levels have proceeded expeditiously due to the availability of resonant ring systems, the testing of high gradient accelerator structures at very high power levels, and the investigation of coupler cavity RF breakdown problems have, typically, been curtailed due to the unavailability of suitable 200 to 300 MW RF test facilities. We describe herein a compact, high peak power amplification system based on a dual hybrid bridge configuration that avoids the need for power splitters at the accelerator dual feed couplers, and also provides a convenient interface for installing high gradient accelerator test structures. Design parameters are presented for a proposed power amplification system that makes use of a 75 MW, 1/2 μs flat-top RF source to produce 280 MW, 1/4 μs flat-top power for testing dual feed TW experimental accelerator sections

  2. Diagnostics Beamline for the SRF Gun Project

    CERN Document Server

    Kamps, T; Goldammer, K; Krämer, Dietrich; Kuske, P; Kuszynski, J; Lipka, D; Marhauser, F; Quast, T; Richter, R

    2005-01-01

    A superconducting rf photo electron injector (SRF gun) is currently under construction by a collaboration between BESSY, DESY, FZR and MBI. The project aims at the design and setup of an CW SRF gun including a diagnostics beamline for the ELBE FEL and to address R&D issues on low emittance injectors for future light sources such as the BESSY FEL. Of critical importance for the injector performance is the control of the electron beam parameters. For this reason a compact diagnostics beamline is under development serving a multitude of operation settings ranging from low-charge (77pC), low-emittance (1 pi mm mrad) mode to high-charge (2.5nC) operation of the gun. For these operation modes beam dynamics simulations are resulting in boundary conditions for the beam instrumentation. Proven and mature technology is projected wherever possible, for example for current and beam position monitoring. The layout of the beam profile and emittance measurement systems is described. For the bunch length, which varies be...

  3. Fabrication of high gradient insulators by stack compression

    Science.gov (United States)

    Harris, John Richardson; Sanders, Dave; Hawkins, Steven Anthony; Norona, Marcelo

    2014-04-29

    Individual layers of a high gradient insulator (HGI) are first pre-cut to their final dimensions. The pre-cut layers are then stacked to form an assembly that is subsequently pressed into an HGI unit with the desired dimension. The individual layers are stacked, and alignment is maintained, using a sacrificial alignment tube that is removed after the stack is hot pressed. The HGI's are used as high voltage vacuum insulators in energy storage and transmission structures or devices, e.g. in particle accelerators and pulsed power systems.

  4. Separation of actinides by high-gradient magnetic filtration

    International Nuclear Information System (INIS)

    Bruns, L.E.; Schliebe, M.J.

    1986-01-01

    High-gradient magnetic filtration has been identified as a candidate solid/liquid separation technique for removing actinide particulate from waste streams. Although HGMS is not intended to reduce the activity in the waste stream to below 100 nCi/g, it does offer two significant advantages: (a) selective removal of TRU solids for subsequent secondary processing and (b) reduced operating complications during solvent extraction due to solids accumulation in the interfacial region. Removal of > 95 wt% of the plutonium and americium solids is expected regardless of the solids present and their properties. Verification tests will be performed to validate this assumption

  5. Cavity Processing and Preparation of 650 MHz Elliptical Cell Cavities for PIP-II

    Energy Technology Data Exchange (ETDEWEB)

    Rowe, Allan [Fermilab; Chandrasekaran, Saravan Kumar [Fermilab; Grassellino, Anna [Fermilab; Melnychuk, Oleksandr [Fermilab; Merio, Margherita [Fermilab; Reid, Thomas [Argonne (main); Sergatskov, Dmitri [Fermilab

    2017-05-01

    The PIP-II project at Fermilab requires fifteen 650 MHz SRF cryomodules as part of the 800 MeV LINAC that will provide a high intensity proton beam to the Fermilab neutrino program. A total of fifty-seven high-performance SRF cavities will populate the cryomodules and will operate in both pulsed and continuous wave modes. These cavities will be processed and prepared for performance testing utilizing adapted cavity processing infrastructure already in place at Fermilab and Argonne. The processing recipes implemented for these structures will incorporate state-of-the art processing and cleaning techniques developed for 1.3 GHz SRF cavities for the ILC, XFEL, and LCLS-II projects. This paper describes the details of the processing recipes and associated chemistry, heat treatment, and cleanroom processes at the Fermilab and Argonne cavity processing facilities. This paper also presents single and multi-cell cavity test results with quality factors above 5·10¹⁰ and accelerating gradients above 30 MV/m.

  6. High-Gradient Test of a 3 GHz Single-Cell Cavity

    CERN Document Server

    Verdú-Andrés, S; Bonomi, R; Degiovanni, A; Garlasché, M; Garonna, A; Mellace, C; Pearce, P; S. Verdú-Andrés; Wegner, R

    2010-01-01

    Pro­ton and car­bon ion beams pre­sent ad­van­ta­geous depth-dose dis­tri­bu­tions with re­spect to X-rays. Car­bon ions allow a bet­ter con­trol of "ra­diore­sis­tant" tu­mours due to their high­er bi­o­log­i­cal re­sponse. For deep-seat­ed tu­mours pro­ton and car­bon ion beams of some nA and en­er­gies of about 200 MeV and 400 MeV/u re­spec­tive­ly are need­ed. For these ap­pli­ca­tions TERA pro­posed the "cy­clinac": a high-fre­quen­cy linac which boosts the hadrons ac­cel­er­at­ed by a cy­clotron. The di­men­sions of the com­plex can be re­duced if high­er ac­cel­er­at­ing gra­di­ents are achieved in the linac. To test the max­i­mum achiev­able fields, a 3 GHz cav­i­ty has been built by TERA. The 19 mm-long cell is fore­seen to be ex­cit­ed at 200 Hz by 3 us RF puls­es and should reach a 40 MV/m ac­cel­er­at­ing gra­di­ent, which cor­re­sponds to a peak sur­face elec­tric field Es of 260 MV/m. In a first high-pow­er test per­for...

  7. Purification of power plant waters with high gradient magnetic filters

    International Nuclear Information System (INIS)

    Rosenberg, R.

    1993-04-01

    This is a report of a literature survey. Magnetic high gradient filtration is suitable for separations in difficult surroundings because it can be used in high pressure and temperature, the filtration can be automated and the filter does not contain components which have to be replaced. Magnetic separators for purification of power plant waters have been manufactured commercially for a long time, but they have not always worked satisfactorily especially when separating small particles. The corrosion products in power plant waters are usually ferrimagnetic or paramagnetic and are well suited for magnetic separation. The particle sizes varies considerable but at least in nuclear power plants they are mostly in the range 0.1-30 μ, some even smaller. According to different publications most 60 Co is in particles, while other publications indicate that more than 70 % is in solution. Similarly the data on the purification efficiency of 60 Co varies significantly. Even small magnetic fields are sufficient to separate large ferrimagnetic particles, but the separation of small and paramagnetic particles requires a field more than 20 kT and the high gradient. Presently available commercial separators are so efficient that its seems not to be economically worthwhile to develop them further to improve the filtration efficiency for small particles. Instead it might be worthwhile to investigate methods to increase the particle size by water chemistry methods. (Au). (25 refs., 2 figs.)

  8. Cold Test Results of the ISAC-II Medium Beta High Gradient Cryomodule

    CERN Document Server

    Laxdal, R E; Clark, G S; Fong, K; Mitra, A K; Poirier, R L; Rawnsley, B; Ries, T; Sekatchev, I; Stanford, G; Zvyagintsev, V

    2004-01-01

    Many proposals (RIA, Eurisol, ISAC-II) are emerging for a new generation of high gradient heavy ion accelerators. The ISAC-II medium beta cryomodule represents the first realized application that encorporates many new techniques to improve the performance over machines presently being used for beam delivery. The machine lattice, compatible with multi-charge acceleration, uses high field (9T) superconducting solenoids with bucking coils for active fringe field compensation. The bulk niobium quarter wave medium beta cavity produces 6 MV/m over an effective length of 18cm with a peak surface field of ~30 MV/m. TRIUMF has developed a mechanical tuner capable of both coarse (kHz) and fine (Hz) frequency adjustments of the cavity. The demonstrated tuner resolution is better than 0.1 μm (0.6 Hz). A new rf coupling loop has been developed that operates at 200 Watts forward power with less than 0.5 Watt of power being added to the helium load. Cold alignment in ISAC-II has been done with rf pick-ups using a ...

  9. Mass, energy and material balances of SRF production process. Part 1: SRF produced from commercial and industrial waste.

    Science.gov (United States)

    Nasrullah, Muhammad; Vainikka, Pasi; Hannula, Janne; Hurme, Markku; Kärki, Janne

    2014-08-01

    This paper presents the mass, energy and material balances of a solid recovered fuel (SRF) production process. The SRF is produced from commercial and industrial waste (C&IW) through mechanical treatment (MT). In this work various streams of material produced in SRF production process are analyzed for their proximate and ultimate analysis. Based on this analysis and composition of process streams their mass, energy and material balances are established for SRF production process. Here mass balance describes the overall mass flow of input waste material in the various output streams, whereas material balance describes the mass flow of components of input waste stream (such as paper and cardboard, wood, plastic (soft), plastic (hard), textile and rubber) in the various output streams of SRF production process. A commercial scale experimental campaign was conducted on an MT waste sorting plant to produce SRF from C&IW. All the process streams (input and output) produced in this MT plant were sampled and treated according to the CEN standard methods for SRF: EN 15442 and EN 15443. The results from the mass balance of SRF production process showed that of the total input C&IW material to MT waste sorting plant, 62% was recovered in the form of SRF, 4% as ferrous metal, 1% as non-ferrous metal and 21% was sorted out as reject material, 11.6% as fine fraction, and 0.4% as heavy fraction. The energy flow balance in various process streams of this SRF production process showed that of the total input energy content of C&IW to MT plant, 75% energy was recovered in the form of SRF, 20% belonged to the reject material stream and rest 5% belonged with the streams of fine fraction and heavy fraction. In the material balances, mass fractions of plastic (soft), plastic (hard), paper and cardboard and wood recovered in the SRF stream were 88%, 70%, 72% and 60% respectively of their input masses to MT plant. A high mass fraction of plastic (PVC), rubber material and non

  10. Plasma processing of superconducting radio frequency cavities

    Science.gov (United States)

    Upadhyay, Janardan

    The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl2 plasma etching mechanism is crucial for achieving the desired modification of Nb SRF cavities. In the process of developing plasma etching technology, an apparatus was built and a method was developed to plasma etch a single cell Pill Box cavity. The plasma characterization was done with the help of optical emission spectroscopy. The Nb etch rate at various points of this cavity was measured before processing the SRF cavity. Cylindrical ring-type samples of Nb placed on the inner surface of the outer wall were used to measure the dependence of the process parameters on plasma etching. The measured etch rate dependence on the pressure, rf power, dc bias, temperature, Cl2 concentration and diameter of the inner electrode was determined. The etch rate mechanism was studied by varying the temperature of the outer wall, the dc bias on the inner electrode and gas conditions. In a coaxial plasma reactor, uniform plasma etching along the cylindrical structure is a challenging task due to depletion of the active radicals along the gas flow direction. The dependence of etch rate uniformity along the cylindrical axis was determined as a function of process parameters. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the

  11. Charged particle beam scanning using deformed high gradient insulator

    Science.gov (United States)

    Chen, Yu -Jiuan

    2015-10-06

    Devices and methods are provided to allow rapid deflection of a charged particle beam. The disclosed devices can, for example, be used as part of a hadron therapy system to allow scanning of a target area within a patient's body. The disclosed charged particle beam deflectors include a dielectric wall accelerator (DWA) with a hollow center and a dielectric wall that is substantially parallel to a z-axis that runs through the hollow center. The dielectric wall includes one or more deformed high gradient insulators (HGIs) that are configured to produce an electric field with an component in a direction perpendicular to the z-axis. A control component is also provided to establish the electric field component in the direction perpendicular to the z-axis and to control deflection of a charged particle beam in the direction perpendicular to the z-axis as the charged particle beam travels through the hollow center of the DWA.

  12. Comparative Studies of High-Gradient Rf and Dc Breakdowns

    CERN Document Server

    Kovermann, Jan Wilhelm; Wuensch, Walter

    2010-01-01

    The CLIC project is based on normal-conducting high-gradient accelerating structures with an average accelerating gradient of 100 MV/m. The maximum achievable gradient in these structures is limited by the breakdown phenomenon. The physics of breakdowns is not yet fully understood quantitatively. A full knowledge could have strong impact on the design, material choice and construction of rf structures. Therefore, understanding breakdowns has great importance to reaching a gradient of 100MV/m with an acceptable breakdown probability. This thesis addresses the physics underlying the breakdown effect, focusing on a comparison of breakdowns in rf structures and in a dc spark setup. The dc system is simpler, easier to benchmark against simulations, with a faster turnaround time, but the relationship to rf breakdown must be established. To do so, an experimental approach based on optical diagnostics and electrical measurements methods was made. Following an introduction into the CLIC project, a general theoretical ...

  13. High gradient magnetic filters for boiler water treatment

    International Nuclear Information System (INIS)

    Harland, J.R.; Nichols, R.M.

    1977-01-01

    Heavy metal oxide suspended solids in those steam condensates recycled to the boilers produce buildup within the boiler tubes which can lead to unequal and reduced heat transfer efficiency, and indirectly, to boiler tube failures. Recommended reductions in such suspended solids in feedwater to the economizers of modern high pressure boilers to levels of under 10 ppb have been published. The industrially-available SALA-HGMF magnetic filter has achieved these desired suspended solids levels in treating steam condensates. The high gradient magnetic filter has been shown in pilot tests to achieve and even exceed the recommended low level suspended solids in a practical and efficient industrial system. Such electromagnetic filters, when combined with good system chemistry, have achieved low single number parts per billion levels of several heavy metals with very high single-pass efficiencies

  14. Status of the LCLS-II Accelerating Cavity Production

    Energy Technology Data Exchange (ETDEWEB)

    Daly, Ed [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Marhauser, Frank [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Fitzpatrick, Jarrod A. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Palczewski, Ari D. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Preble, Joe [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Wilson, Katherine M. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Grimm, C. J. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Burrill, Andrew B. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gonnella, Daniel [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2017-05-01

    Cavity serial production for the LCLS-II 4 GeV CM SRF linac has started. A quantity of 266 accelerating cavities has been ordered from two industrial vendors. Jefferson Laboratory leads the cavity procurement activities for the project and has successfully transferred the Nitrogen-Doping process to the industrial partners in the initial phase, which is now being applied for the production cavities. We report on the results from vendor qualification and the status of the cavity production for LCLS-II.

  15. Electron bunch train excited higher-order modes in a superconducting RF cavity

    Science.gov (United States)

    Gao, Yong-Feng; Huang, Sen-Lin; Wang, Fang; Feng, Li-Wen; Zhuang, De-Hao; Lin, Lin; Zhu, Feng; Hao, Jian-Kui; Quan, Sheng-Wen; Liu, Ke-Xin

    2017-04-01

    Higher-order mode (HOM) based intra-cavity beam diagnostics has been proved effective and convenient in superconducting radio-frequency (SRF) accelerators. Our recent research shows that the beam harmonics in the bunch train excited HOM spectrum, which have much higher signal-to-noise ratio than the intrinsic HOM peaks, may also be useful for beam diagnostics. In this paper, we will present our study on bunch train excited HOMs, including a theoretical model and recent experiments carried out based on the DC-SRF photoinjector and SRF linac at Peking University. Supported by National Natural Science Foundation of China (11275014)

  16. Mass, energy and material balances of SRF production process. Part 2: SRF produced from construction and demolition waste.

    Science.gov (United States)

    Nasrullah, Muhammad; Vainikka, Pasi; Hannula, Janne; Hurme, Markku; Kärki, Janne

    2014-11-01

    In this work, the fraction of construction and demolition waste (C&D waste) complicated and economically not feasible to sort out for recycling purposes is used to produce solid recovered fuel (SRF) through mechanical treatment (MT). The paper presents the mass, energy and material balances of this SRF production process. All the process streams (input and output) produced in MT waste sorting plant to produce SRF from C&D waste are sampled and treated according to CEN standard methods for SRF. Proximate and ultimate analysis of these streams is performed and their composition is determined. Based on this analysis and composition of process streams their mass, energy and material balances are established for SRF production process. By mass balance means the overall mass flow of input waste material stream in the various output streams and material balances mean the mass flow of components of input waste material stream (such as paper and cardboard, wood, plastic (soft), plastic (hard), textile and rubber) in the various output streams of SRF production process. The results from mass balance of SRF production process showed that of the total input C&D waste material to MT waste sorting plant, 44% was recovered in the form of SRF, 5% as ferrous metal, 1% as non-ferrous metal, and 28% was sorted out as fine fraction, 18% as reject material and 4% as heavy fraction. The energy balance of this SRF production process showed that of the total input energy content of C&D waste material to MT waste sorting plant, 74% was recovered in the form of SRF, 16% belonged to the reject material and rest 10% belonged to the streams of fine fraction and heavy fraction. From the material balances of this process, mass fractions of plastic (soft), paper and cardboard, wood and plastic (hard) recovered in the SRF stream were 84%, 82%, 72% and 68% respectively of their input masses to MT plant. A high mass fraction of plastic (PVC) and rubber material was found in the reject material

  17. Three-dimensional self-consistent simulations of multipacting in superconducting radio frequency cavities. Final Report

    International Nuclear Information System (INIS)

    Nieter, Chet

    2010-01-01

    Superconducting radio frequency (SRF) cavities are a popular choice among researchers designing new accelerators because of the reduced power losses due to surface resistance. However, SRF cavities still have unresolved problems, including the loss of power to stray electrons. Sources of these electrons are field emission from the walls and ionization of background gas, but the predominant source is secondary emission yield (SEY) from electron impact. When the electron motion is in resonance with the cavity fields the electrons strike the cavity surface repeatedly creating a resonant build up of electrons referred to as multipacting. Cavity shaping has successfully reduced multipacting for cavities used in very high energy accelerators. However, multipacting is still a concern for the cavity power couplers, where shaping is not possible, and for cavities used to accelerate particles at moderate velocities. This Phase II project built upon existing models in the VORPAL simulation framework to allow for simulations of multipacting behavior in SRF cavities and their associated structures. The technical work involved allowed existing models of secondary electron generation to work with the complex boundary conditions needed to model the cavity structures. The types of data produced by VORPAL were also expanded to include data common used by cavity designers to evaluate cavity performance. Post-processing tools were also modified to provide information directly related to the conditions that produce multipacting. These new methods were demonstrated by running simulations of a cavity design being developed by researchers at Jefferson National Laboratory to attempt to identify the multipacting that would be an issue for the cavity design being considered. These simulations demonstrate that VORPAL now has the capabilities to assist researchers working with SRF cavities to understand and identify possible multipacting issues with their cavity designs.

  18. Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by TEM and EELS

    OpenAIRE

    Trenikhina, Y.; Romanenko, A.; Kwon, J.; Zuo, J. -M.; Zasadzinski, J. F.

    2015-01-01

    Nanoscale defect structure within the magnetic penetration depth of ~100nm is key to the performance limitations of niobium superconducting radio frequency (SRF) cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride for...

  19. On active disturbance rejection based control design for superconducting RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, John; Morris, Dan; Usher, Nathan [National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, East Lansing, MI 48824-1321 (United States); Gao, Zhiqiang, E-mail: z.gao@csuohio.edu [Center for Advanced Control Technologies, Fenn College of Engineering, Cleveland State University, Cleveland, OH 44115-2214 (United States); Zhao Shen; Nicoletti, Achille; Zheng Qinling [Center for Advanced Control Technologies, Fenn College of Engineering, Cleveland State University, Cleveland, OH 44115-2214 (United States)

    2011-07-01

    Superconducting RF (SRF) cavities are key components of modern linear particle accelerators. The National Superconducting Cyclotron Laboratory (NSCL) is building a 3 MeV/u re-accelerator (ReA3) using SRF cavities. Lightly loaded SRF cavities have very small bandwidths (high Q) making them very sensitive to mechanical perturbations whether external or self-induced. Additionally, some cavity types exhibit mechanical responses to perturbations that lead to high-order non-stationary transfer functions resulting in very complex control problems. A control system that can adapt to the changing perturbing conditions and transfer functions of these systems would be ideal. This paper describes the application of a control technique known as 'Active Disturbance Rejection Control' (ARDC) to this problem.

  20. Comparison of Deformation in High-Purity Single/Large Grain and Polycrystalline Niobium Superconducting Cavities

    International Nuclear Information System (INIS)

    Ganapati Rao Myneni; Peter Kneisel

    2005-01-01

    The current approach for the fabrication of superconducting radio frequency (SRF) cavities is to roll and deep draw sheets of polycrystalline high-purity niobium. Recently, a new technique was developed at Jefferson Laboratory that enables the fabrication of single-crystal high-purity Nb SRF cavities. To better understand the differences between SRF cavities fabricated out of fine-grained polycrystalline sheet in the standard manner and single crystal cavities fabricated by the new technique, two half-cells were produced according to the two different procedures and compared using a variety of analytical techniques including optical microscopy, scanning laser confocal microscopy, profilometry, and X-ray diffraction. Crystallographic orientations, texture, and residual stresses were determined in the samples before and after forming and this poster presents the results of this ongoing study

  1. Ignition and monitoring technique for plasma processing of multicell superconducting radio-frequency cavities

    Science.gov (United States)

    Doleans, Marc

    2016-12-01

    An in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help remove adsorbed gases on the RF surface, and to reduce its secondary emission yield. SNS SRF cavities have six accelerating cells and the plasma typically ignites in the cell where the electric field is the highest. This article details the technique to ignite and monitor the plasma in each cell of the SNS cavities.

  2. Role of thermal resistance on the performance of superconducting radio frequency cavities

    Science.gov (United States)

    Dhakal, Pashupati; Ciovati, Gianluigi; Myneni, Ganapati Rao

    2017-03-01

    Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF) cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q0(Bp) curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q0(Bp) .

  3. Role of thermal resistance on the performance of superconducting radio frequency cavities

    Directory of Open Access Journals (Sweden)

    Pashupati Dhakal

    2017-03-01

    Full Text Available Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q_{0}(B_{p} curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q_{0}(B_{p}.

  4. Multipacting in a coaxial coupler with bias voltage for SRF operation with a large beam current

    Science.gov (United States)

    Liu, Z.-K.; Wang, Ch.; Chang, F.-Y.; Chang, L.-H.; Chang, M.-H.; Chen, L.-J.; Chung, F.-T.; Lin, M.-C.; Lo, C.-H.; Tsai, C.-L.; Tsai, M.-H.; Yeh, M.-S.; Yu, T.-C.

    2016-09-01

    A superconducting radio-frequency (SRF) module is commonly used for a high-energy accelerator; its purpose is to provide energy to the particle beam. Because of the low power dissipation and smaller impedance of a higher-order mode for this module, it can provide more power to the particle beam with better stability through decreasing the couple bunch instability. A RF coupler is necessary to transfer the high power from a RF generator to the cavity. A coupler of coaxial type is a common choice. With high-power operation, it might suffer from multipacting, which is a resonance phenomenon due to re-emission of secondary electrons. Applying a bias voltage between inner and outer conductors of the coaxial coupler might increase or decrease the strength of the multipacting effect. We studied the effect of a bias voltage on multipacting using numerical simulation to track the motion of the electrons. The simulation results and an application for SRF operation with a large beam current are presented in this paper.

  5. Higher order mode damping in a five-cell superconducting rf cavity with a photonic band gap coupler cell

    Science.gov (United States)

    Arsenyev, Sergey A.; Temkin, Richard J.; Shchegolkov, Dmitry Yu.; Simakov, Evgenya I.; Boulware, Chase H.; Grimm, Terry L.; Rogacki, Adam R.

    2016-08-01

    We present a study of higher order mode (HOM) damping in the first multicell superconducting radio-frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving higher average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery linacs (ERLs). Beam current in ERLs is limited by the beam breakup instability, caused by parasitic HOMs interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The five-cell cavity with a PBG cell was designed and optimized for HOM damping. Monopole and dipole HOMs were simulated. The SRF cavity was fabricated and tuned. External quality factors for some HOMs were measured in a cold test. The measurements agreed well with the simulations.

  6. Higher order mode damping in a five-cell superconducting rf cavity with a photonic band gap coupler cell

    Directory of Open Access Journals (Sweden)

    Sergey A. Arsenyev

    2016-08-01

    Full Text Available We present a study of higher order mode (HOM damping in the first multicell superconducting radio-frequency (SRF cavity with a photonic band gap (PBG coupler cell. Achieving higher average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery linacs (ERLs. Beam current in ERLs is limited by the beam breakup instability, caused by parasitic HOMs interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The five-cell cavity with a PBG cell was designed and optimized for HOM damping. Monopole and dipole HOMs were simulated. The SRF cavity was fabricated and tuned. External quality factors for some HOMs were measured in a cold test. The measurements agreed well with the simulations.

  7. High gradient magnetic separation applied to environmental remediation

    International Nuclear Information System (INIS)

    Prenger, F.C.; Stewart, W.F.; Hill, D.D.; Avens, L.R.; Worl, L.A.; Schake, A.; de Aguero, K.J.; Padilla, D.D.; Tolt, T.L.

    1993-01-01

    High Gradient Magnetic Separation (HGMS) is an application of superconducting magnet technology to the separation of magnetic solids from other solids, liquids, or gases. The production of both high magnetic fields (>4 T) and large field gradients using superconducting magnet technology has made it possible to separate a previously unreachable but large family of paramagnetic materials. This is a powerful technique that can be used to separate widely dispersed contaminants from a host material and may be the only technique available for separating material in the colloidal state. Because it is a physical separation process, no additional waste is generated. We are applying this technology to the treatment of radioactive wastes for environmental remediation. We have conducted tests examining slurries containing nonradioactive, magnetic surrogates. Results from these studies were used to verify our analytical model of the separation process. The model describes the rate process for magnetic separation and is based on a force balance on the paramagnetic species. This model was used to support bench scale experiments and prototype separator design

  8. Avoiding vacuum arcs in high gradient normal conducting RF structures

    CERN Document Server

    Sjøbæk, Kyrre Ness; Adli, Erik; Grudiev, Alexej; Wuensch, Walter

    In order to build the Compact LInear Collider (CLIC), accelerating structures reaching extremely high accelerating gradients are needed. Such structures have been built and tested using normal-conducting copper, powered by X-band RF power and reaching gradients of 100 MV/m and above. One phenomenon that must be avoided in order to reliably reach such gradients, is vacuum arcs or “breakdowns”. This can be accomplished by carefully designing the structure geometry such that high surface fields and large local power flows are avoided. The research presented in this thesis presents a method for optimizing the geometry of accelerating structures so that these breakdowns are made less likely, allowing the structure to operate reliably at high gradients. This was done primarily based on a phenomenological scaling model, which predicted the maximum gradient as a function of the break down rate, pulse length, and field distribution in the structure. The model is written in such a way that it allows direct comparis...

  9. Multi-MW K-Band Harmonic Multiplier: RF Source For High-Gradient Accelerator R & D

    Science.gov (United States)

    Solyak, N. A.; Yakovlev, V. P.; Kazakov, S. Yu.; Hirshfield, J. L.

    2009-01-01

    A preliminary design is presented for a two-cavity harmonic multiplier, intended as a high-power RF source for use in experiments aimed at developing high-gradient structures for a future collider. The harmonic multiplier is to produce power at selected frequencies in K-band (18-26.5 GHz) using as an RF driver an XK-5 S-band klystron (2.856 GHz). The device is to be built with a TE111 rotating mode input cavity and interchangeable output cavities running in the TEn11 rotating mode, with n = 7,8,9 at 19.992, 22.848, and 25.704 GHz. An example for a 7th harmonic multiplier is described, using a 250 kV, 20 A injected laminar electron beam; with 10 MW of S-band drive power, 4.7 MW of 20-GHz output power is predicted. Details are described of the magnetic circuit, cavities, and output coupler.

  10. High intensity SRF proton linac workshop (vugraphs)

    International Nuclear Information System (INIS)

    Rusnak, B.A.

    1995-01-01

    The meeting is divided into four sections. The first section is the general introduction and included opening remarks and an overview of APT (accelerator product of tritium). The second section contains vugraphs from the cavity-structures working group. The third section is comprised of vugraphs from the couplers and rf working group. And the fourth section contains vugraphs of the system integration group

  11. Hybrid Physical Chemical Vapor Deposition of Superconducting Magnesium Diboride Coatings for Large Scale Radio Frequency Cavities

    Science.gov (United States)

    Lee, Namhoon; Withanage, Wenura; Tan, Teng; Wolak, Matthaeus; Xi, Xiaoxing

    2016-03-01

    Magnesium diboride (MgB2) is considered to be a great candidate for next generation superconducting radio frequency (SRF) cavities due to its higher critical temperature Tc (40 K) and increased thermodynamic critical field Hc compared to other conventional superconductors. These properties significantly reduce the BCS surface resistance (RsBCS)and residual resistance (Rres) according to theoretical studies and suggest the possibility of an enhanced accelerating field (Eacc) . We have investigated the possibility of coating the inner surface of a 3 GHz SRF cavity with MgB2 by using a hybrid physical-vapor deposition (HPCVD) system which was modified for this purpose. To simulate a real 3 GHz SRF cavity, a stainless steel mock cavity has been employed for the study. The film quality was characterized on small substrates that were placed at selected locations within the cavity. MgB2 films on stainless steel foils, niobium pieces and SiC substrates showed transition temperatures of above 36 K. Dielectric resonance measurements resulted in promising Q values as obtained for the MgB2 films grown on the various substrates. By employing the HPCVD technique, a uniform film was achieved across the cavity interior, demonstrating the feasibility of HPCVD for MgB2 coatings for SRF cavities.

  12. Coaxial two-channel high-gradient dielectric wakefield accelerator

    Directory of Open Access Journals (Sweden)

    G. V. Sotnikov

    2009-06-01

    Full Text Available A new scheme for a dielectric wakefield accelerator is proposed that employs a cylindrical multizone dielectric structure configured as two concentric dielectric tubes with outer and inner vacuum channels for drive and accelerated bunches. Analytical and numerical studies have been carried out for such coaxial dielectric-loaded structures (CDS for high-gradient acceleration. An analytical theory of wakefield excitation by particle bunches in a multizone CDS has been formulated. Numerical calculations are presented for an example of a CDS using dielectric tubes with dielectric permittivity 5.7, having external diameters of 2.121 and 0.179 mm with inner diameters of 2.095 and 0.1 mm. An annular 5 GeV, 6 nC electron bunch with rms length of 0.035 mm energizes a wakefield on the structure axis having an accelerating gradient of ∼600  MeV/m with a transformer ratio ∼8∶1. The period of the accelerating field is ∼0.33  mm. If the width of the drive bunch channel is decreased, it is possible to obtain an accelerating gradient of >1  GeV/m while keeping the transformer ratio approximately the same. Full numerical simulations using a particle-in-cell code have confirmed results of the linear theory and furthermore have shown the important influence of the quenching wave that restricts the region of the wakefield to within several periods following the drive bunch. Numerical simulations for another example have shown nearly stable transport of drive and accelerated bunches through the CDS, using a short train of drive bunches.

  13. Use of high gradient magnetic separation for actinide application

    International Nuclear Information System (INIS)

    Avens, L.R.; Worl, L.A.; Padilla, D.D.

    1996-01-01

    Decontamination of materials such as soils or waste water that contain radioactive isotopes, heavy metals, or hazardous components is a subject of great interest. Magnetic separation is a physical separation process that segregates materials on the basis of magnetic susceptibility. Because the process relies on physical properties, separations can be achieved while producing a minimum of secondary waste. Most traditional physical separation processes effectively treat particles larger than 70 microns. In many situations, the radioactive contaminants are found concentrated in the fine particle size fraction of less than 20 microns. For effective decontamination of the fine particle size fraction most current operations resort to chemical dissolution methods for treatment. High gradient magnetic separation (HGMS) is able to effectively treat particles from 90 to ∼0.1 micron in diameter. The technology is currently used on the 60 ton per hour scale in the kaolin clay industry. When the field gradient is of sufficiently high intensity, paramagnetic particles can be physically captured and separated from extraneous nonmagnetic material. Because all actinide compounds are paramagnetic, magnetic separation of actinide containing mixtures is feasible. The advent of reliable superconducting magnets also makes magnetic separation of weakly paramagnetic species attractive. HGMS work at Los Alamos National Laboratory (LANL) is being developed for soil remediation, waste water treatment and treatment of actinide chemical processing residues. LANL and Lockheed Environmental Systems and Technologies Company (LESAT) have worked on a co-operative research and development agreement (CRADA) to develop HGMS for radioactive soil decontamination. The program is designed to transfer HGMS from the laboratory and other industries for the commercial treatment of radioactive contaminated materials. 9 refs., 2 figs., 2 tabs

  14. End design of the SSC 58 mm High Gradient Quadrupole

    International Nuclear Information System (INIS)

    Caspi, S.

    1992-01-01

    The ''end'' design of the High Gradient Quad. was done with consideration to the integrated field harmonics, the iron contribution, and the maximum field at the conductor. Magnetic analysis was done on the return end only, however the physical dimension of the lead end were determined as well. Using the cross-section of the windings and Cook's program BEND, we generated the physical end windings around the return end. Placing a single wire at the center of each turn the integrated gradient was computed and iterating on the end block spacers the integrated harmonics minimized. The final geometry was then used for more, extensive calculations, such as the field at the conductor and the 3D field harmonics. For this detailed calculation we have placed a single line current at the center of each strand and included the iron contribution (μ = ∞), see Appendix C. With the termination of the iron serving as a reference, the maximum length of the inner and outer layers are 182 mm and 215 mm respectively. The magnetic length of the end was computed from the gradient function A 2 and was found to be 142 mm. In reality we expect the physical length of the end to be somewhat larger, however this should have little or no effect on the magnetic length. The gradient in the straight section is 212.44 T/m at 7000 A and the integrated value of the gradient is -3.01665 E5 (G) in the end region marked by the magnetic length of the end. The respective integrated harmonics for the end 12 pole and 20 pole are -10.6658 (G/CM 4 ) and 0.7279 (G/cm 8 ) corresponding to b 6 = 0.351 , b 10 = -0.024 units. The above was computed from the values of A 2 , A 6 , and A 10

  15. Electron color centers in SrF2-Na crystals

    International Nuclear Information System (INIS)

    Kachan, S.I.; Chornij, Z.P.

    2006-01-01

    A radiation-induced memory effect in SrF 2 -Na crystals is studied. It was shown that optical bleaching of M + A color centers at 80 K in SrF 2 -Na crystals causes the core of an M + A -center to transform into the V + a Me + V + a configuration, in which all three point defects are arranged diagonally in the cube cell. Reirradiation of an optically bleached crystal by X-rays generates F D centers in it. The F D →M + A transformation in SrF 2 -Na crystals occurs at T = 135 K, in contrast to the F A →M + A transformations, which take place at T > 200 K [ru

  16. Control System Design for Automatic Cavity Tuning Machines

    Energy Technology Data Exchange (ETDEWEB)

    Carcagno, R.; Khabiboulline, T.; Kotelnikov, S.; Makulski, A.; Nehring, R.; Nogiec, J.; Ross, M.; Schappert, W.; /Fermilab; Goessel, A.; Iversen, J.; Klinke, D.; /DESY

    2009-05-01

    A series of four automatic tuning machines for 9-cell TESLA-type cavities are being developed and fabricated in a collaborative effort among DESY, FNAL, and KEK. These machines are intended to support high-throughput cavity fabrication for construction of large SRF-based accelerator projects. Two of these machines will be delivered to cavity vendors for the tuning of XFEL cavities. The control system for these machines must support a high level of automation adequate for industrial use by non-experts operators. This paper describes the control system hardware and software design for these machines.

  17. Control System Design for Automatic Cavity Tuning Machines

    International Nuclear Information System (INIS)

    Carcagno, R.; Khabiboulline, T.; Kotelnikov, S.; Makulski, A.; Nehring, R.; Nogiec, J.; Ross, M.; Schappert, W.; Goessel, A.; Iversen, J.; Klinke, D.

    2009-01-01

    A series of four automatic tuning machines for 9-cell TESLA-type cavities are being developed and fabricated in a collaborative effort among DESY, FNAL, and KEK. These machines are intended to support high-throughput cavity fabrication for construction of large SRF-based accelerator projects. Two of these machines will be delivered to cavity vendors for the tuning of XFEL cavities. The control system for these machines must support a high level of automation adequate for industrial use by non-experts operators. This paper describes the control system hardware and software design for these machines.

  18. HOM Survey of the First CEBAF Upgrade Style Cavity Pair

    International Nuclear Information System (INIS)

    Marhauser, Frank; Daly, Edward; Davis, G.; Drury, Michael; Grenoble, Christiana; Hogan, John; Manus, Robert; Preble, Joseph; Reece, Charles; Rimmer, Robert; Tian, Kai; Wang, Haipeng

    2009-01-01

    The planned upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Laboratory (JLab) requires ten new superconducting rf (SRF) cavity cryomodules to double the beam energy to the envisaged 12 GeV. Adequate cavity Higher Order Mode (HOM) suppression is essential to avoid multipass, multibunch beam break-up (BBU) instabilities of the recirculating beam. We report on detailed HOM surveys performed for the first two upgrade style cavities tested in a dedicated cavity pair cryomodule at 2K. The safety margin to the BBU threshold budget at 12 GeV has been assessed.

  19. Review of ingot niobium as a material for superconducting radiofrequency accelerating cavities

    Energy Technology Data Exchange (ETDEWEB)

    Kneisel, P., E-mail: kneisel@jlab.org [Jefferson Lab, Newport News, VA 23606 (United States); Ciovati, G.; Dhakal, P. [Jefferson Lab, Newport News, VA 23606 (United States); Saito, K. [Michigan State University, East Lansing, MI 48824 (United States); Singer, W.; Singer, X. [DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Myneni, G.R., E-mail: rao@jlab.org [Jefferson Lab, Newport News, VA 23606 (United States)

    2015-02-21

    As a result of collaboration between Jefferson Lab and niobium manufacturer Companhia Brasileira de Metalurgia e Mineração (CBMM), ingot niobium was explored as a possible material for superconducting radiofrequency (SRF) cavity fabrication. The first single cell cavity from large-grain high purity niobium was fabricated and successfully tested at Jefferson Lab in 2004. This work triggered research activities in other SRF laboratories around the world. Large-grain (LG) niobium became not only an interesting alternative material for cavity builders, but also material scientists and surface scientists were eager to participate in the development of this technology. Many single cell cavities made from material of different suppliers have been tested successfully and several multi-cell cavities have shown performances comparable to the best cavities made from standard fine-grain niobium. Several 9-cell cavities fabricated by Research Instruments and tested at DESY exceeded the best performing fine grain cavities with a record accelerating gradient of E{sub acc}=45.6 MV/m. The quality factor of those cavities was also higher than that of fine-grain (FG) cavities processed with the same methods. Such performance levels push the state-of-the art of SRF technology and are of great interest for future accelerators. This contribution reviews the development of ingot niobium technology and highlights some of the differences compared to standard FG material and opportunities for further developments.

  20. Material Selection and Characterization for High Gradient RF Applications

    CERN Document Server

    Arnau-Izquierdo, G; Heikkinen, S; Ramsvik, T; Sgobba, Stefano; Taborelli, M; Wuensch, W

    2007-01-01

    The selection of candidate materials for the accelerating cavities of the Compact Linear Collider (CLIC) is carried out in parallel with high power RF testing. The maximum DC breakdown field of copper, copper alloys, refractory metals, aluminium and titanium have been measured with a dedicated setup. Higher maximum fields are obtained for refractory metals and for titanium, which exhibits, however, important damages after conditioning. Fatigue behaviour of copper alloys has been studied for surface and bulk by pulsed laser irradiation and ultrasonic excitation, respectively. The selected copper alloys show consistently higher fatigue resistance than copper in both experiments. In order to obtain the best local properties in the device a possible solution is a bi-metallic assembly. Junctions of molybdenum and copper-zirconium UNS C15000 alloy, achieved by HIP (Hot Isostatic Pressing) diffusion bonding or explosion bonding were evaluated for their mechanical strength. The reliability of the results obtained wit...

  1. Pengaruh variasi rasio HAF/SRF terhadap sifat vulkanisat NBR

    Directory of Open Access Journals (Sweden)

    Ihda Novia Indrajati

    2012-12-01

    Full Text Available The objectives of the research were to study the effect of HAF/SRF black ratio and the loading of sulfur on vulcanization characteristic, swelling behaviour and compression set of NBR vulcanizates. The ratio of HAF/SRF were 0/70; 10/60; 20/50; 30/40; 35/35; 40/30; 50/20 and 70/0 phr, respectively. The observation of this research consist of curing characteristic, morphology property and swelling equilibrium. Curing characteristic was determined from cure rate index (CRI, vulcanizates morphology was studied by SEM and swelling equilibrium was conducted by immersion test using benzene. The data were analyzed qualitatively to see the respond of the variable on physical properties. The curing characteristic of double filler vulcanizates was higher than those with single filler. Solvent uptake for double filler present in between to those with HAF or SRF. All of vulcanizates indicate the anomalous mass tranfer, with n>0,5 and constant k showed the same trend. The intrinsic diffusivity (D*, sorption and permeation coefficient showed similar trend and the maximum was obtained by the ratio HAF/SRF 0/70.

  2. Near-field microwave magnetic nanoscopy of superconducting radio frequency cavity materials

    Science.gov (United States)

    Tai, Tamin; Ghamsari, Behnood G.; Bieler, Thomas R.; Tan, Teng; Xi, X. X.; Anlage, Steven M.

    2014-06-01

    A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two measurements are performed to demonstrate these capabilities with a near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high Residual-Resistance-Ratio bulk Nb sample showing strong localized nonlinear response, with surface RF magnetic field Bsurface˜102 mT. The second is a raster scanned harmonic response image on a MgB2 thin film demonstrating a uniform nonlinear response over large areas.

  3. High-gradient two-beam electron accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L. [Omega-P, Inc., New Haven, CT (United States)

    2014-11-04

    The main goal for this project was to design, build, and evaluate a detuned-cavity, collinear, two-beam accelerator structure. Testing was to be at the Yale University Beam Physics Laboratory, under terms of a sub-grant from Omega-P to Yale. Facilities available at Yale for this project include a 6-MeV S-band RF gun and associated beam line for forming and transporting a ~1 A drive beam , a 300 kV beam source for use as a test beam, and a full panoply of laboratory infrastructure and test equipment. During the first year of this project, availability and functionality of the 6-MeV drive beam and 300 kV test beam were confirmed, and the beam line was restored to a layout to be used with the two-beam accelerator project. Major efforts during the first year were also focused on computational design and simulation of the accelerator structure itself, on beam dynamics, and on beam transport. Effort during the second year was focussed on building and preparing to test the structure, including extensive cold testing. Detailed results from work under this project have been published in twelve archival journal articles, listed in Section IV of the technical report.

  4. Mechanical design and engineering of the 3.9 GHZ, 3rd harmonic SRF system at Fermilab

    International Nuclear Information System (INIS)

    Don Mitchell

    2004-01-01

    The mechanical development of the 3.9 GHz, 3rd Harmonic SRF System is summarized to include: the development of a full scale copper prototype cavity structure; the design of the niobium 3 cell and niobium 9 cell structures; the design of the helium vessel and cryostat; the HOM coupler design; and a preliminary look at the main coupler design. The manufacturing processes for forming, rolling, and e-beam welding the HOM coupler, cavity cells, and end tubes are also described. Due to the exotic materials and manufacturing processes used in this type of device, a cost estimate for the material and fabrication is provided. The 3rd harmonic design is organized via a web-based data management approach

  5. Mechanical design and engineering of the 3.9 GHZ, 3rd harmonic SRF system at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Don Mitchell et al.

    2004-08-05

    The mechanical development of the 3.9 GHz, 3rd Harmonic SRF System is summarized to include: the development of a full scale copper prototype cavity structure; the design of the niobium 3 cell and niobium 9 cell structures; the design of the helium vessel and cryostat; the HOM coupler design; and a preliminary look at the main coupler design. The manufacturing processes for forming, rolling, and e-beam welding the HOM coupler, cavity cells, and end tubes are also described. Due to the exotic materials and manufacturing processes used in this type of device, a cost estimate for the material and fabrication is provided. The 3rd harmonic design is organized via a web-based data management approach.

  6. Analytical and semi-analytical formalism for the voltage and the current sources of a superconducting cavity under dynamic detuning

    CERN Document Server

    Doleans, M

    2003-01-01

    Elliptical superconducting radio frequency (SRF) cavities are sensitive to frequency detuning because they have a high Q value in comparison with normal conducting cavities and weak mechanical properties. Radiation pressure on the cavity walls, microphonics, and tuning system are possible sources of dynamic detuning during SRF cavity-pulsed operation. A general analytic relation between the cavity voltage, the dynamic detuning function, and the RF control function is developed. This expression for the voltage envelope in a cavity under dynamic detuning and dynamic RF controls is analytically expressed through an integral formulation. A semi-analytical scheme is derived to calculate the voltage behavior in any practical case. Examples of voltage envelope behavior for different cases of dynamic detuning and RF control functions are shown. The RF control function for a cavity under dynamic detuning is also investigated and as an application various filling schemes are presented.

  7. Application of superconducting magnesium diboride (MGB2) in superconducting radio frequency cavities

    Science.gov (United States)

    Tan, Teng

    The superconductivity in magnesium diboride (MgB2) was discovered in 2001. As a BCS superconductor, MgB2 has a record-high Tc of 39 K, high Jc of > 107 A/cm2 and no weak link behavior across the grain boundary. All these superior properties endorsed that MgB2 would have great potential in both power applications and electronic devices. In the past 15 years, MgB2 based power cables, microwave devices, and commercial MRI machines emerged and the next frontier are superconducting radio frequency (SRF) cavities. SRF cavities are one of the leading accelerator technologies. In SRF cavities, applied microwave power generates electrical fields that accelerate particle beams. Compared with other accelerator techniques, SRF cavity accelerators feature low loss, high acceleration gradients and the ability to accelerate continuous particle beams. However, current SRF cavities are made from high-purity bulk niobium and work at 2 K in superfluid helium. The construction and operational cost of SRF cavity accelerators are very expensive. The demand for SRF cavity accelerators has been growing rapidly in the past decade. Therefore, a lot of effort has been devoted to the enhancement of the performance and the reduction of cost of SRF cavities. In 2010, an acceleration gradient of over 50 MV/m has been reported for a Nb-based SRF cavity. The magnetic field at the inner surface of such a cavity is ~ 1700 Oe, which is close to the thermodynamic critical field of Nb. Therefore, new materials and technologies are required to raise the acceleration gradient of future SRF cavity accelerators. Among all the proposed approaches, using MgB2 thin films to coat the inner surface of SRF cavities is one of the promising tactics with the potential to raise both the acceleration gradient and the operation temperature of SRF cavity accelerators. In this work, I present my study on MgB2 thin films for their application in SRF cavities. C-epitaxial MgB2 thin films grown on SiC(0001) substrates

  8. Analysis of the Qualification-Tests Performance of the Superconducting Cavities for the SNS Linac

    CERN Document Server

    Delayen, J R; Ozelis, O

    2004-01-01

    Thomas Jefferson National Accelerating Facility (Jefferson Lab) is producing superconducting radio frequency (SRF) cryomodules for the Spallation Neutron Source (SNS) cold linac. This consists of 11 medium-beta (β=0.61) cyomodules of 3 cavities each, and 12 high-beta (β=0.81) cryomodules of 4 cavities each. Before assembly into cavity strings the cavities undergo individual qualification tests in a vertical cryostat (VTA). In this paper we analyze the performance of the cavities during these qualification tests, and attempt to correlate this performance with cleaning, assembly, and testing procedures. We also compare VTA performance with performance in completed cryomodules.

  9. Particle capture efficiency in a multi-wire model for high gradient magnetic separation

    KAUST Repository

    Eisenträ ger, Almut; Vella, Dominic; Griffiths, Ian M.

    2014-01-01

    High gradient magnetic separation (HGMS) is an efficient way to remove magnetic and paramagnetic particles, such as heavy metals, from waste water. As the suspension flows through a magnetized filter mesh, high magnetic gradients around the wires

  10. Fundamental Study of Micro-Defects in Electropolished EB-Welded and Hydroformed SRF Accelerating Structures

    Energy Technology Data Exchange (ETDEWEB)

    Sumption, Mike

    2014-08-29

    In the area of niobium elecropolishing fundamentals, we focused on understanding the influence of the surface topology, and geometry (with effects from gravity included. The formation of a viscous film is essential for the electropolishing process to take place. The exact nature and composition of the film formed on niobium is still unknown because of its solubility in the electrolyte. Extensive pitting may take place at surface where a stable film cannot form. This has to be taken into consideration while determining the speed with which the SRF cavities are rotated while EP. Hydrodynamic aspects must be taken into consideration while optimizing the polishing parameters. There is improvement in surface finish with polishing time. There is a huge change in surface quality when the EP time is increased from 2 hours to 4 hours but not much change takes place when the time is further increased to 6 hours. So keeping the economic points in view, about 100 um defect layer removal may be sufficient to get the desired performance. In the area of Electropolishing of untreated and treated niobium with Weld Joints we studied untreated and treated Nb, especially for the heat affected areas next to welded bumps, electropolished for different durations. The electropolishing of the untreated Nb caused the formation of pits on the surface at about 15 min but they disappeared when the electropolishing duration was more than 15 min. Electropolishing for 120 min smoothened the surface of untreated Nb by levelling the surface, but the severe formation of pits on the whole surface was found after 240 min. The treatment of Nb significantly changed the Nb surface morphology which was covered by grains of different size that looked light or dark in the optical microscope. The treated Nb was susceptible to pitting during the entire electropolishing starting from 15 min and the dark grains had more susceptibility to pitting than the light grains. In addition, electropolishing for 240 min

  11. Operating experience with superconducting cavities at Jefferson Lab

    International Nuclear Information System (INIS)

    Reece, C.E.

    1998-01-01

    The CEBAF recirculating superconducting electron linac at Jefferson Lab is now in full operation supporting nuclear physics experiments in three target halls at up to 4.4 GeV. The 330 SRF cavities, operating at 2.0 K, continue to perform well above design specifications, and have accumulated over 8,000,000 operating cavity hours. The authors have to date no evidence of degradation of cavity performance. The SRF cavities have demonstrated excellent reliability. The one klystron per cavity design provides CEBAF with flexibility and redundancy for normal operations. Several techniques have been developed for establishing optimum operating conditions for the 330 independent systems. Operation of the cavities and control systems at the full design current of 1 mA has recently been achieved. The principal constraints on usable gradient for low current operations are (1) discharge at the cold ceramic rf window induced by electron field emission in cavities, (2) tuner controls, and (3) stability of the waveguide vacuum in the region between the warm and cold windows. Several cryomodules have been improved by application of rf helium processing while installed on the beamline

  12. Testing a GaAs cathode in SRF gun

    International Nuclear Information System (INIS)

    Wang, E.; Kewisch, J.; Ben-Zvi, I.; Burrill, A.; Rao, T.; Wu, Q.; Holmes, D.

    2011-01-01

    RF electron guns with a strained superlattice GaAs cathode are expected to generate polarized electron beams of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode's surface and lower cathode temperature. We plan to install a bulk GaAs:Cs in a SRF gun to evaluate the performance of both the gun and the cathode in this environment. The status of this project is: In our 1.3 GHz 1/2 cell SRF gun, the vacuum can be maintained at nearly 10 -12 Torr because of cryo-pumping at 2K. With conventional activation of bulk GaAs, we obtained a QE of 10% at 532 nm, with lifetime of more than 3 days in the preparation chamber and have shown that it can survive in transport from the preparation chamber to the gun. The beam line has been assembled and we are exploring the best conditions for baking the cathode under vacuum. We report here the progress of our test of the GaAs cathode in the SRF gun. Future particle accelerators, such as eRHIC and the ILC require high-brightness, high-current polarized electrons. Strained superlattice GaAs:Cs has been shown to be an efficient cathode for producing polarized electrons. Activation of GaAs with Cs,O(F) lowers the electron affinity and makes it energetically possible for all the electrons, excited into the conduction band that drift or diffuse to the emission surface, to escape into the vacuum. Presently, all operating polarized electron sources, such as the CEBAF, are DC guns. In these devices, the excellent ultra-high vacuum extends the lifetime of the cathode. However, the low field gradient on the photocathode's emission surface of the DC guns limits the beam quality. The higher accelerating gradients, possible in the RF guns, generate a far better beam. Until recently, most RF guns operated at room temperature, limiting the vacuum to ∼10 -9 Torr. This destroys the GaAs's NEA surface. The SRF guns combine the excellent vacuum conditions of DC guns and the high accelerating

  13. Elemental balance of SRF production process: solid recovered fuel produced from municipal solid waste.

    Science.gov (United States)

    Nasrullah, Muhammad; Vainikka, Pasi; Hannula, Janne; Hurme, Markku; Oinas, Pekka

    2016-01-01

    In the production of solid recovered fuel (SRF), certain waste components have excessive influence on the quality of product. The proportion of rubber, plastic (hard) and certain textiles was found to be critical as to the elemental quality of SRF. The mass flow of rubber, plastic (hard) and textiles (to certain extent, especially synthetic textile) components from input waste stream into the output streams of SRF production was found to play the decisive role in defining the elemental quality of SRF. This paper presents the mass flow of polluting and potentially toxic elements (PTEs) in SRF production. The SRF was produced from municipal solid waste (MSW) through mechanical treatment (MT). The results showed that of the total input chlorine content to process, 55% was found in the SRF and 30% in reject material. Of the total input arsenic content, 30% was found in the SRF and 45% in fine fraction. In case of cadmium, lead and mercury, of their total input content to the process, 62%, 38% and 30%, respectively, was found in the SRF. Among the components of MSW, rubber material was identified as potential source of chlorine, containing 8.0 wt.% of chlorine. Plastic (hard) and textile components contained 1.6 and 1.1. wt.% of chlorine, respectively. Plastic (hard) contained higher lead and cadmium content compared with other waste components, i.e. 500 mg kg(-1) and 9.0 mg kg(-1), respectively. © The Author(s) 2015.

  14. EFFECTIVENESS OF FERTILIZER SRF-N D AND H ON RICE GROWTH AND RESULTS

    Directory of Open Access Journals (Sweden)

    Nasruddin Razak

    2014-02-01

    Full Text Available Study aims are to know effectiveness level of SRF-N (D & H on growth and yield of lowland rice, and gets fertilizer dosage that gave highest yield of lowland rice. Twelve 12 treatments added with recommendation dosage and farmer treatment. Experiment arranged in RCBD three replications. Result: SRF-N significantly effect growth and yield of lowland rice. Applied SRF-N type H with dosage 350 kg per ha which combined SP-36 and KCl gave higher dry grind grain compared to other treatments of SRF. Proposes SRF-H 280 kg and SRF-D 500 kg per ha. Treatment of farmer way with dosage Urea 300 kg, SP-36 100 kg, and KCl 50 kg per ha, gave higher dry grind grain (8.14 t DGG per ha compared to other treatments including recommendation dosage (7.65 t DGG per ha. Effectiveness of SRF-N type H with dosage 350 kg (two times applications on produce of grain, is 0.97 times compared to recommendation. Need to study more of SRF-H 350 kg and 280 kg per ha, and SRF-H 500 kg per ha (two times application which combined with P and K recommendation on different location and planting season to obtain accurate data in order to obtain locationspecific fertilizer recommendation

  15. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    Science.gov (United States)

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-09-01

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.

  16. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    International Nuclear Information System (INIS)

    Ford, Denise C; Cooley, Lance D; Seidman, David N

    2013-01-01

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium–hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities. (paper)

  17. A Study of Thermocurrent Induced Magnetic Fields in ILC Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Anthony C. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Cooley, Victoria [Univ. of Wisconsin, Madison, WI (United States)

    2014-03-31

    The case of axisymmetric ILC-type cavities with titanium helium vessels is investigated. A first-order estimate for magnetic field within the SRF current layer is presented. The induced magnetic field is found to be not more than 1.4x10-8 Tesla = 0.14 milligauss for the case of axial symmetry. Magnetic fields due to symmetry breaking effects are discussed.

  18. Mechanical Design and Fabrication Studies for SPL Superconducting RF Cavities

    CERN Document Server

    Atieh, S; Aviles Santillana, I; Capatina, O; Renaglia, T; Tardy, T; Valverde Alonso, N; Weingarten, W

    2011-01-01

    CERN’s R&D programme on the Superconducting Proton Linac’s (SPL) superconducting radio frequency (SRF) elliptical cavities made from niobium sheets explores new mechanical design and consequently new fabrication methods, where several opportunities for improved optimization were identified. A stainless steel helium vessel is under design rather than a titanium helium vessel using an integrated brazed transition between Nb and the SS helium vessel. Different design and fabrication aspects were proposed and the results are discussed hereafter.

  19. Microphonics Testing of the CEBAF Upgrade 7-Cell Cavity

    International Nuclear Information System (INIS)

    G.K. Davis; J.R. Delayen; M. Drury; T. Hiatt; C. Hovater; T. Powers; J. Preble

    2001-01-01

    An upgrade cryomodule is being developed for CEBAF at Jefferson Lab. In support of this effort, vibration testing was performed on a single SRF cavity at cryogenic temperature in a Horizontal Test Bed. The tests included response to excitation from background vibration, swept sinusoids, high-power RF pulses, and mechanical impulses. Test procedures, apparatus, and results are presented, along with a description of planned follow-up tests

  20. Superconducting Radio-Frequency Cavities for Low-Beta Particle Accelerators

    Science.gov (United States)

    Kelly, Michael

    2012-01-01

    High-power proton and ion linac projects based on superconducting accelerating cavities are driving a worldwide effort to develop and build superconducting cavities for beta < 1. Laboratories and institutions building quarter-wave, halfwave and single- or multi-spoke cavities continue to advance the state of the art for this class of cavities, and the common notion that low-beta SRF cavities fill a need in niche applications and have low performance is clearly no longer valid. This article reviews recent developments and results for SC cavity performance for cavities with beta up to approximately 0.5. The considerable ongoing effort on reduced beta elliptical cell cavities is not discussed. An overview of associated subsystems required to operate low-beta cavities, including rf power couplers and fast and slow tuners, is presented.

  1. Physical and mechanical metallurgy of high purity Nb for accelerator cavities

    International Nuclear Information System (INIS)

    Bieler, T.R.; Wright, N.T.; Pourboghrat, F.; Compton, C.; Hartwig, K.T.; Baars, D.; Zamiri, A.; Chandrasekaran, S.; Darbandi, P.; Jiang, H.; Skoug, E.; Balachandran, S.; Ice, G.E.; Liu, W.

    2010-01-01

    In the past decade, high Q values have been achieved in high purity Nb superconducting radio frequency (SRF) cavities. Fundamental understanding of the physical metallurgy of Nb that enables these achievements is beginning to reveal what challenges remain to establish reproducible and cost-effective production of high performance SRF cavities. Recent studies of dislocation substructure development and effects of recrystallization arising from welding and heat treatments and their correlations with cavity performance are considered. With better fundamental understanding of the effects of dislocation substructure evolution and recrystallization on electron and phonon conduction, as well as the interior and surface states, it will be possible to design optimal processing paths for cost-effective performance using approaches such as hydroforming, which minimizes or eliminates welds in a cavity.

  2. Flux pinning characteristics in cylindrical niobium samples used for superconducting radio frequency cavity fabrication

    Science.gov (United States)

    Dhavale, Asavari S.; Dhakal, Pashupati; Polyanskii, Anatolii A.; Ciovati, Gianluigi

    2012-06-01

    We present the results from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low-temperature baking as they are typically applied to SRF cavities. The magnetization data are analyzed using a modified critical state model. The critical current density Jc and pinning force Fp are calculated from the magnetization data and their temperature dependence and field dependence are presented. The LG samples have lower critical current density and pinning force density compared to FG samples, favorable to lower flux trapping efficiency. This effect may explain the lower values of residual resistance often observed in LG cavities than FG cavities.

  3. Towards a Cryogen-Free MgB2-Based Superconducting Radio Frequency Accelerating Cavities

    Science.gov (United States)

    Nassiri, Alireza

    Studies on the application of Magnesium diboride (MgB2) superconducting films have shown promise for use with the radio-frequency (SRF) accelerating cavities. MgB2\\ coating is a potential candidate to replace bulk niobium (Nb) SRF cavities. The ultimate goal of our research is to demonstrate MgB2 coating on copper cavities to allow operation at about 20 K or so as a result of the high transition temperature (Tc) of MgB2 and taking advantage of the excellent thermal conductivity of copper. Here, we will report on our recent experimental results of applying hybrid physical-chemical vapor deposition (HPCVD) to grow MgB2 films on 2-inch diameter copper discs as well as on a 2.8 GHz resonator cavity *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06H11357.

  4. Flux pinning characteristics in cylindrical ingot niobium used in superconducting radio frequency cavity fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Dhavale Ashavai, Pashupati Dhakal, Anatolii A Polyanskii, Gianluigi Ciovati

    2012-04-01

    We present the results of from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low temperature baking as they are typically applied to SRF cavities. The magnetization data were fitted using a modified critical state model. The critical current density Jc and pinning force Fp are calculated from the magnetization data and their temperature dependence and field dependence are presented. The LG samples have lower critical current density and pinning force density compared to FG samples which implies a lower flux trapping efficiency. This effect may explain the lower values of residual resistance often observed in LG cavities than FG cavities.

  5. Flux pinning characteristics in cylindrical niobium samples used for superconducting radio frequency cavity fabrication

    International Nuclear Information System (INIS)

    Dhavale, Asavari S; Dhakal, Pashupati; Ciovati, Gianluigi; Polyanskii, Anatolii A

    2012-01-01

    We present the results from DC magnetization and penetration depth measurements of cylindrical bulk large-grain (LG) and fine-grain (FG) niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities. The surface treatment consisted of electropolishing and low-temperature baking as they are typically applied to SRF cavities. The magnetization data are analyzed using a modified critical state model. The critical current density J c and pinning force F p are calculated from the magnetization data and their temperature dependence and field dependence are presented. The LG samples have lower critical current density and pinning force density compared to FG samples, favorable to lower flux trapping efficiency. This effect may explain the lower values of residual resistance often observed in LG cavities than FG cavities. (paper)

  6. Physical and mechanical metallurgy of high purity Nb for accelerator cavities

    Directory of Open Access Journals (Sweden)

    T. R. Bieler

    2010-03-01

    Full Text Available In the past decade, high Q values have been achieved in high purity Nb superconducting radio frequency (SRF cavities. Fundamental understanding of the physical metallurgy of Nb that enables these achievements is beginning to reveal what challenges remain to establish reproducible and cost-effective production of high performance SRF cavities. Recent studies of dislocation substructure development and effects of recrystallization arising from welding and heat treatments and their correlations with cavity performance are considered. With better fundamental understanding of the effects of dislocation substructure evolution and recrystallization on electron and phonon conduction, as well as the interior and surface states, it will be possible to design optimal processing paths for cost-effective performance using approaches such as hydroforming, which minimizes or eliminates welds in a cavity.

  7. Dental cavities

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/001055.htm Dental cavities To use the sharing features on this page, please enable JavaScript. Dental cavities are holes (or structural damage) in the ...

  8. X-ray imaging of superconducting radio frequency cavities

    Science.gov (United States)

    Musser, Susan Elizabeth

    The goal of this research was to develop an improved diagnostic technique to identify the location of defects that limit superconducting radio frequency (SRF) cavity performance during cavity testing or in existing accelerators. SRF cavities are primarily constructed of niobium. Electrons within the metal of a cavity under high electric field gradient have a probability of tunneling through the potential barrier. i e. leave the surface or are field emitted in regions where defects are encountered. Field emitted electrons are accelerated in the electric fields within the cavity. The electrons can have complicated trajectories and strike the cavity walls thus producing x-rays via Coulomb interactions and/or bremsstrahlung radiation. The endpoint energy of an x-ray spectrum predicts the electron maximum final kinetic energy within the cavity. Field emission simulations can then predict the source of the field-emitted electrons and the defect(s). In a multicell cavity the cells are coupled together and act as a set of coupled oscillators. There are multiple passbands of excitation for a multicell structure operating in a particular mode. For different passbands of operation the direction and amplitude of the fields within a cavity change from that of the normal accelerating mode. Field emitted electrons have different trajectories depending on the mode and thus produce x-rays in different locations. Using a collimated sodium iodide detector and subjecting a cavity to multiple passband modes at high electric field gradient the source of a cavity's x-rays can be determined. Knowing the location of the x-rays and the maximum electron kinetic energy; field emission simulations for different passband modes can be used to determine and verify the source of the field emitted electrons from mode to mode. Once identified, the defect(s) can be repaired or modifications made to the manufacturing process.

  9. Fabrication and Testing of Deflecting Cavities for APS

    Energy Technology Data Exchange (ETDEWEB)

    Mammosser, John; Wang, Haipeng; Rimmer, Robert; Jim, Henry; Katherine, Wilson; Dhakal, Pashupati; Ali, Nassiri; Jim, Kerby; Jeremiah, Holzbauer; Genfa, Wu; Joel, Fuerst; Yawei, Yang; Zenghai, Li

    2013-09-01

    Jefferson Lab (Newport News, Virginia) in collaboration with Argonne National Laboratory (Argonne, IL) has fabricated and tested four first article, 2.8 GHz, deflecting SRF cavities, for Argonne's Short-Pulse X-ray (SPX) project. These cavities are unique in many ways including the fabrication techniques in which the cavity cell and waveguides were fabricated. These cavity subcomponents were milled from bulk large grain niobium ingot material directly from 3D CAD files. No forming of sub components was used with the exception of the beam-pipes. The challenging cavity and helium vessel design and fabrication results from the stringent RF performance requirements required by the project and operation in the APS ring. Production challenges and fabrication techniques as well as testing results will be discussed in this paper.

  10. Characterization of an SRF gun: a 3D full wave simulation

    International Nuclear Information System (INIS)

    Wang, E.; Ben-Zvi, I.; Wang, J.

    2011-01-01

    We characterized a BNL 1.3GHz half-cell SRF gun is tested for GaAs photocathode. The gun already was simulated several years ago via two-dimensional (2D) numerical codes (i.e., Superfish and Parmela) with and without the beam. In this paper, we discuss our investigation of its characteristics using a three dimensional (3D) full-wave code (CST STUDIO SUITE(trademark)).The input/pickup couplers are sited symmetrically on the same side of the gun at an angle of 180 o . In particular, the inner conductor of the pickup coupler is considerably shorter than that of the input coupler. We evaluated the cross-talk between the beam (trajectory) and the signal on the input coupler compared our findings with published results based on analytical models. The CST STUDIO SUITE(trademark) also was used to predict the field within the cavity; particularly, a combination of transient/eigenmode solvers was employed to accurately construct the RF field for the particles, which also includes the effects of the couplers. Finally, we explored the beam's dynamics with a particle in cell (PIC) simulation, validated the results and compare them with 2D code result.

  11. Breaking and Moving Hotspots in a Large Grain Nb Cavity with a Laser Beam

    International Nuclear Information System (INIS)

    Ciovati, G.; Cheng, G.; Flood, R. J.; Jordan, K.; Kneisel, P.; Morrone, M. L.; Turlington, L.; Wilson, K. M.; Zhang, S.; Anlage, S. M.; Gurevich, A. V.; Nemes, G.; Baldwin, C.

    2011-01-01

    Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported

  12. Tests on MgB2 for Application to SRF Cavities

    International Nuclear Information System (INIS)

    Tajima, T.; Canabal, A.; Los Alamos; Zhao, Y.; Wollongong U.; Romanenko, A.; Cornell U., LNS; Nantista, C.; Tantawi, S.; SLAC; Phillips, L.; Jefferson Lab; Iwashita, Y.; Kyoto U., Inst. Chem. Res.; Campisi, I.; Oak Ridge; Moeckly, B.; Superconductor Tech., Santa Barbara

    2006-01-01

    Magnesium diboride (MgB 2 ) has a transition temperature (T c ) of ∼40 K, i.e., about 4 times higher than niobium (Nb). Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (R s ) than Nb at 4 K and seems to have much less power dependence than high-T c materials such as YBCO. However, it was also found that it will depend on the way you deposit the film. The result from on-axis pulsed laser deposition (PLD) showed rapid increase in R s with higher surface magnetic fields compared to the film deposited with reactive evaporation method

  13. Photographic guidance for selecting flow resistance coefficients in high-gradient channels

    Science.gov (United States)

    Steven E. Yochum; Francesco Comiti; Ellen Wohl; Gabrielle C. L. David; Luca Mao

    2014-01-01

    Photographic guidance is presented to assist with the estimation of Manning’s n and Darcy-Weisbach f in high-gradient plane-bed, step-pool, and cascade channels. Reaches both with and without instream wood are included. These coefficients are necessary for the estimation of reachaverage velocity, energy loss, and...

  14. Static high-gradient magnetic fields affect the functionality of monocytic cells

    Czech Academy of Sciences Publication Activity Database

    Syrovets, T.; Schmidt, Z.; Buechele, B.; Zablotskyy, Vitaliy A.; Dejneka, Alexandr; Dempsey, N.; Simmet, T.

    2014-01-01

    Roč. 28, č. 1 (2014), s. 1-2 ISSN 0892-6638 Institutional support: RVO:68378271 Keywords : static high-gradient * magnet ic fields * affect the functionality * monocytic cells Subject RIV: BM - Solid Matter Physics ; Magnet ism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.)

  15. How a high-gradient magnetic field could affect cell life

    Czech Academy of Sciences Publication Activity Database

    Zablotskyy, Vitaliy A.; Polyakova, Tetyana; Lunov, Oleg; Dejneka, Alexandr

    2016-01-01

    Roč. 6, Nov (2016), 1-12, č. článku 37407. ISSN 2045-2322 Grant - others:AV ČR(CZ) Fellowship J. E. Purkyně Institutional support: RVO:68378271 Keywords : high-gradient magnetic field * cell Subject RIV: BO - Biophysics Impact factor: 4.259, year: 2016

  16. Status of superconducting RF cavity development

    International Nuclear Information System (INIS)

    Shepard, K.W.

    1989-01-01

    For several reasons, a brief historical review seems appropriate at this time. The twenty-fifth anniversary of the first acceleration of beam with a superconducting cavity will occur shortly [1,2,3]. Also, the scope of accelerator applications of superconducting radio-frequency (SRF) devices has, within the last few months, begun to increase rapidly [4] - to the point that it seems likely that early expectations for this technology will largely be fulfilled. Since the object is to accelerate beam, a simple one parameter measure of the technology is the total of how much beam has been accelerated. Figure 1 shows the total accumulated voltage in tests and/or operation of superconducting accelerating cavities with beam, up to the time indicated, as reported in the open literature [4-35]. This parameter has been divided into two terms: first, the subtotal for electron accelerating velocity-of-light structures, and second the subtotal for low-velocity, ion accelerating structures. To restate: each of these terms represents as a function of time an integrated, accumulative total voltage produced by SRF hardware and demonstrated with beam. 56 refs., 4 figs

  17. Understanding Quality Factor Degradation in Superconducting Niobium Cavities at Low Microwave Field Amplitudes

    Science.gov (United States)

    Romanenko, A.; Schuster, D. I.

    2017-12-01

    In niobium superconducting radio frequency (SRF) cavities for particle acceleration, a decrease of the quality factor at lower fields—a so-called low field Q slope or LFQS—has been a long-standing unexplained effect. By extending the high Q measurement techniques to ultralow fields, we discover two previously unknown features of the effect: (i) saturation at rf fields lower than Eacc˜0.1 MV /m ; (ii) strong degradation enhancement by growing thicker niobium pentoxide. Our findings suggest that the LFQS may be caused by the two level systems in the natural niobium oxide on the inner cavity surface, thereby identifying a new source of residual resistance and providing guidance for potential nonaccelerator low-field applications of SRF cavities.

  18. Plasma Etching of superconducting radio frequency cavity by Ar/Cl2 capacitively coupled Plasma

    Science.gov (United States)

    Upadhyay, Janardan; Popovic, Svetozar; Valente-Feliciano, Anne-Marie; Phillips, Larry; Vuskovic, Lepsha

    2016-09-01

    We are developing plasma processing technology of superconducting radio frequency (SRF) cavities. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the asymmetry was studied by changing the contour of the inner electrode. The optimized contour of the electrode based on these measurements was chosen for SRF cavity processing. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity is used, which previously mechanically polished, buffer chemically etched afterwards and rf tested at cryogenic temperatures for a baseline test. Plasma processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise manner to establish segmented plasma processing. The cavity is rf tested afterwards at cryogenic temperatures. The rf test and surface condition results are presented.

  19. Large grain CBMM Nb ingot slices: An ideal test bed for exploring the microstructure-electromagnetic property relationships relevant to SRF

    International Nuclear Information System (INIS)

    Sung, Zu-Hawn; Lee, Peter J.; Polyanskii, Anatolii; Balachandran, Shreyas; Chetri, Santosh; Larbalestier, David C.; Wang, Mingmin; Compton, Christopher; Bieler, Thomas R.

    2015-01-01

    High purity (RRR > 200), large grain (> 5-10 cm) niobium ingot slices have been successfully used to fabricate radio frequency (RF) cavities for particle accelerators. They offer significantly reduced fabrication cost by eliminating processing steps and furthermore they provide the opportunity to study the influence of individual grain boundaries in SRF Nb. Here we summarize our measurements of grain boundary (GB) effects on the superconducting properties of large grain high purity niobium sheet manufactured by CBMM. We show by magneto-optical (MO) imaging that GBs allow premature flux penetration, but only when they are oriented close to the direction of the magnetic field. However, even low angle GBs produced by minor deformations commensurate with half-cell forming produce localized flux penetration. The transport properties of grain boundaries were investigated by direct transport across them and evidence for preferential vortex flow along the GBs of SRF Nb was observed for the first time. Using transmission electron microscopy (TEM) and micro crystallographic analysis with electron backscattered diffraction (EBSD), we were able to quantitatively characterize surface substructures that can lead to localized thermal breakdown of superconductivity. Important to these studies was the development of sample preparation techniques that made the cutout single, bi-crystal and tri-crystal Nb coupons as representative as possible of the surface properties of cavities manufactured by standard techniques

  20. New Methods for Thin Film Deposition and First Investigations of the use of High Temperature Superconductors for Thin Film Cavities

    CERN Document Server

    Gustafsson, Anna; Vollenberg, Wilhelmus; Seviour, Rebecca

    2010-01-01

    Niobium thin film cavities have shown good and reliable performance for LEP and LHC, although there are limitations to overcome if this technique should be used for new accelerators such as the ILC. New coating techniques like High Power Impulse Magnetron Sputtering (HiPIMS) has shown very promising results and we will report on its possible improvements for Nb thin film cavity performance. Current materials used in accelerator Superconducting Radio Frequency (SRF) technologies operate at temperatures below 4 K, which require complex cryogenic systems. Researchers have investigated the use of High Temperature Superconductors (HTS) to form RF cavities, with limited success. We propose a new approach to achieve a high-temperature SRF cavity based on the superconducting ’proximity effect’. The superconducting proximity effect is the effect through which a superconducting material in close proximity to a non-superconducting material induces a superconducting condensate in the latter. Using this effect we hope...

  1. Vibrational Stability of SRF Accelerator Test Facility at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    McGee, M.W.; Volk, J.T.; /Fermilab

    2009-05-01

    Recently developed, the Superconducting Radio Frequency (SRF) Accelerator Test Facilities at Fermilab support the International Linear Collider (ILC), High Intensity Neutrino Source (HINS), a new high intensity injector (Project X) and other future machines. These facilities; Meson Detector Building (MDB) and New Muon Lab (NML) have very different foundations, structures, relative elevations with respect to grade level and surrounding soil composition. Also, there are differences in the operating equipment and their proximity to the primary machine. All the future machines have stringent operational stability requirements. The present study examines both near-field and ambient vibration in order to develop an understanding of the potential contribution of near-field sources (e.g. compressors, ultra-high and standard vacuum equipment, klystrons, modulators, utility fans and pumps) and distant noise sources to the overall system displacements. Facility vibration measurement results and methods of possible isolation from noise sources are presented and discussed.

  2. Turn-key SRF accelerators to drive subcritical reactors

    International Nuclear Information System (INIS)

    Johnson, Rolland P.

    2011-01-01

    Large particle accelerator projects, both accomplished and proposed, have been used to engage US industry through contracts and grants to develop efficient capabilities to design, develop, produce, and deliver entire accelerator systems or any needed subsystems. Staffed in many cases by experienced scientists and engineers from National Laboratories and Universities, existing companies could extend their portfolios to offer turn-key accelerators with parameters to match the needs of ADS. If the reactors were based on molten salt fuel such that trip rate requirements were relaxed, the developments needed for a multi-MW proton accelerator for ADS would be minimal. Turn-key SRF proton linacs for ADS operation can be ordered now to enable GW-level power generation from natural thorium, natural uranium, or nuclear waste from conventional reactors. (author)

  3. Adaptive Feedforward Cancellation of Sinusoidal Disturbances in Superconducting RF Cavities

    CERN Document Server

    Kandil, T H; Hartung, W; Khalil, H; Popielarski, J; Vincent, J; York, R C

    2004-01-01

    A control method, known as adaptive feedforward cancellation (AFC) is applied to damp sinusoidal disturbances due to microphonics in superconducting RF (SRF) cavities. AFC provides a method for damping internal, and external sinusoidal disturbances with known frequencies. It is preferred over other schemes because it uses rudimentary information about the frequency response at the disturbance frequencies, without the necessity of knowing an analytic model (transfer function) of the system. It estimates the magnitude and phase of the sinusoidal disturbance inputs and generates a control signal to cancel their effect. AFC, along with a frequency estimation process, is shown to be very successful in the cancellation of sinusoidal signals from different sources. The results of this research may significantly reduce the power requirements and increase the stability for lightly loaded continuous-wave SRF systems.

  4. Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity

    OpenAIRE

    Xin Zhao; G. Ciovati; T. R. Bieler

    2010-01-01

    The performance of superconducting radio-frequency (SRF) resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots”) were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD), and optical micro...

  5. Ultra-High Gradient S-band Linac for Laboratory and Industrial Applications

    Science.gov (United States)

    Faillace, L.; Agustsson, R.; Dolgashev, V.; Frigola, P.; Murokh, A.; Rosenzweig, J.; Yakimenko, V.

    2010-11-01

    A strong demand for high gradient structures arises from the limited real estate available for linear accelerators. RadiaBeam Technologies is developing a Doubled Energy Compact Accelerator (DECA) structure: an S-band standing wave electron linac designed to operate at accelerating gradients of up to 50 MV/m. In this paper, we present the radio-frequency design of the DECA S-band accelerating structure, operating at 2.856 GHz in the π-mode. The structure design is heavily influenced by NLC collaboration experience with ultra high gradient X-band structures; S-band, however, is chosen to take advantage of commonly available high power S-band klystrons.

  6. A high-gradient high-duty-factor Rf photo-cathode electron gun

    International Nuclear Information System (INIS)

    Rimmer, Robert A.; Hartman, Neal; Lidia, Steven M.; Wang, Shaoheng

    2002-01-01

    We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure

  7. A high-gradient high-duty-factor RF photo-cathode electron gun

    International Nuclear Information System (INIS)

    Rimmer, Robert; Hartman, N.; Lidia, S.; Wang, S.H.

    2002-01-01

    We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure

  8. Design Studies of Nb3Sn High-Gradient Quadrupole Models for LARP

    International Nuclear Information System (INIS)

    Andreev, Nikolai; Caspi, Shlomo; Dietderich, Daniel; Ferracin, Paolo; Ghosh, Arup; Kashikhin, Vadim; Lietzke, Al; Novitski, Igor; Zlobin, Alexander; McInturff, Alfred; Sabbi, GianLuca

    2007-01-01

    Insertion quadrupoles with large aperture and high gradient are required to achieve the luminosity upgrade goal of 10 35 cm -2 s -1 at the Large Hadron Collider (LHC). In 2004, the US Department of Energy established the LHC Accelerator Research Program (LARP) to develop a technology base for the upgrade. Nb 3 Sn conductor is required in order to operate at high field and with sufficient temperature margin. We report here on the conceptual design studies of a series of 1 m long 'High-gradient Quadrupoles' (HQ) that will explore the magnet performance limits in terms of peak fields, forces and stresses. The HQ design is expected to provide coil peak fields of more than 15 T, corresponding to gradients above 300 T/m in a 90 mm bore. Conductor requirements, magnetic, mechanical and quench protection issues for candidate HQ designs will be presented and discussed

  9. Efficient inclusion body processing using chemical extraction and high gradient magnetic fishing

    DEFF Research Database (Denmark)

    Heebøll-Nielsen, Anders; Choe, W.S.; Middelberg, A.P.J.

    2003-01-01

    of the product-loaded supports with the aid of high gradient magnetic fields. The manufacture and testing of two types of micron-sized nonporous superparamagnetic metal chelator particles derivatized with iminodiacetic acid is described. In small-scale adsorption studies conducted with a hexahistidine tagged...... at a 60-fold increased scale using the high gradient magnetic fishing (HGMF) system to collect loaded Cu2+-chelator particles following batch adsorption of L1. Over 70% of the initial Ll present was recovered within the HGMF rig in a highly clarified form in two batch elution cycles with an overall......In this study we introduce a radical new approach for the recovery of proteins expressed in the form of inclusion bodies, involving W chemical extraction from the host cells, (ii) adsorptive capture of the target protein onto small magnetic adsorbents, and (iii) subsequent rapid collection...

  10. Superparamagnetic adsorbents for high-gradient magnetic fishing of lectins out of legume extracts

    DEFF Research Database (Denmark)

    Heebøll-Nielsen, Anders; Dalkiær, M.; Hubbuch, Jürgen

    2004-01-01

    This work presents the development, testing, and application in high-gradient magnetic fishing of superparamagnetic supports for adsorption of lectins. Various approaches were examined to produce affinity, mixed mode, and hydrophobic charge induction type adsorbents. In clean monocomponent systems...... affinity supports created by direct attachment of glucose or maltose to amine-terminated iron oxide particles could bind concanavalin A at levels of up to approximate to 280 mg g(-1) support with high affinity (approximate to 1 muM dissociation constants). However, the best performance was delivered......-linked adsorbents supplied sufficient competition to dissolved sugars to selectively bind concanavalin A in an extract of jack beans. The dextran-linked supports were employed in a high-gradient magnetic fishing experiment, in which concanavalin A was purified to near homogeneity from a crude, unclarified extract...

  11. The suitability of using dissolved gases to determine groundwater discharge to high gradient streams

    Science.gov (United States)

    Gleeson, Tom; Manning, Andrew H.; Popp, Andrea; Zane, Mathew; Clark, Jordan F.

    2018-01-01

    Determining groundwater discharge to streams using dissolved gases is known to be useful over a wide range of streamflow rates but the suitability of dissolved gas methods to determine discharge rates in high gradient mountain streams has not been sufficiently tested, even though headwater streams are critical as ecological habitats and water resources. The aim of this study is to test the suitability of using dissolved gases to determine groundwater discharge rates to high gradient streams by field experiments in a well-characterized, high gradient mountain stream and a literature review. At a reach scale (550 m) we combined stream and groundwater radon activity measurements with an in-stream SF6 tracer test. By means of numerical modeling we determined gas exchange velocities and derived very low groundwater discharge rates (∼15% of streamflow). These groundwater discharge rates are below the uncertainty range of physical streamflow measurements and consistent with temperature, specific conductance and streamflow measured at multiple locations along the reach. At a watershed-scale (4 km), we measured CFC-12 and δ18O concentrations and determined gas exchange velocities and groundwater discharge rates with the same numerical model. The groundwater discharge rates along the 4 km stream reach were highly variable, but were consistent with the values derived in the detailed study reach. Additionally, we synthesized literature values of gas exchange velocities for different stream gradients which show an empirical relationship that will be valuable in planning future dissolved gas studies on streams with various gradients. In sum, we show that multiple dissolved gas tracers can be used to determine groundwater discharge to high gradient mountain streams from reach to watershed scales.

  12. The suitability of using dissolved gases to determine groundwater discharge to high gradient streams

    Science.gov (United States)

    Gleeson, Tom; Manning, Andrew H.; Popp, Andrea; Zane, Matthew; Clark, Jordan F.

    2018-02-01

    Determining groundwater discharge to streams using dissolved gases is known to be useful over a wide range of streamflow rates but the suitability of dissolved gas methods to determine discharge rates in high gradient mountain streams has not been sufficiently tested, even though headwater streams are critical as ecological habitats and water resources. The aim of this study is to test the suitability of using dissolved gases to determine groundwater discharge rates to high gradient streams by field experiments in a well-characterized, high gradient mountain stream and a literature review. At a reach scale (550 m) we combined stream and groundwater radon activity measurements with an in-stream SF6 tracer test. By means of numerical modeling we determined gas exchange velocities and derived very low groundwater discharge rates (∼15% of streamflow). These groundwater discharge rates are below the uncertainty range of physical streamflow measurements and consistent with temperature, specific conductance and streamflow measured at multiple locations along the reach. At a watershed-scale (4 km), we measured CFC-12 and δ18O concentrations and determined gas exchange velocities and groundwater discharge rates with the same numerical model. The groundwater discharge rates along the 4 km stream reach were highly variable, but were consistent with the values derived in the detailed study reach. Additionally, we synthesized literature values of gas exchange velocities for different stream gradients which show an empirical relationship that will be valuable in planning future dissolved gas studies on streams with various gradients. In sum, we show that multiple dissolved gas tracers can be used to determine groundwater discharge to high gradient mountain streams from reach to watershed scales.

  13. Development of High-Gradient Dielectric Laser-Driven Particle Accelerator Structures

    Energy Technology Data Exchange (ETDEWEB)

    Byer, Robert L. [Stanford Univ., CA (United States). Edward L. Ginzton Lab.

    2013-11-07

    The thrust of Stanford's program is to conduct research on high-gradient dielectric accelerator structures driven with high repetition-rate, tabletop infrared lasers. The close collaboration between Stanford and SLAC (Stanford Linear Accelerator Center) is critical to the success of this project, because it provides a unique environment where prototype dielectric accelerator structures can be rapidly fabricated and tested with a relativistic electron beam.

  14. accelerating cavity

    CERN Multimedia

    On the inside of the cavity there is a layer of niobium. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment.

  15. High-gradient breakdown studies of an X-band Compact Linear Collider prototype structure

    Directory of Open Access Journals (Sweden)

    Xiaowei Wu

    2017-05-01

    Full Text Available A Compact Linear Collider prototype traveling-wave accelerator structure fabricated at Tsinghua University was recently high-gradient tested at the High Energy Accelerator Research Organization (KEK. This X-band structure showed good high-gradient performance of up to 100  MV/m and obtained a breakdown rate of 1.27×10^{−8} per pulse per meter at a pulse length of 250 ns. This performance was similar to that of previous structures tested at KEK and the test facility at the European Organization for Nuclear Research (CERN, thereby validating the assembly and bonding of the fabricated structure. Phenomena related to vacuum breakdown were investigated and are discussed in the present study. Evaluation of the breakdown timing revealed a special type of breakdown occurring in the immediately succeeding pulse after a usual breakdown. These breakdowns tended to occur at the beginning of the rf pulse, whereas usual breakdowns were uniformly distributed in the rf pulse. The high-gradient test was conducted under the international collaboration research program among Tsinghua University, CERN, and KEK.

  16. High-gradient operators in the psl(2 vertical stroke 2) Gross-Neveu model

    International Nuclear Information System (INIS)

    Cagnazzo, Alessandra; Schomerus, Volker; Tlapak, Vaclav

    2014-10-01

    It has been observed more than 25 years ago that sigma model perturbation theory suffers from strongly RG-relevant high-gradient operators. The phenomenon was first seen in 1-loop calculations for the O(N) vector model and it is known to persist at least to two loops. More recently, Ryu et al. suggested that a certain deformation of the psl(N vertical stroke N) WZNW-model at level k=1, or equivalently the psl(N vertical stroke N) Gross-Neveu model, could be free of RG-relevant high-gradient operators and they tested their suggestion to leading order in perturbation theory. In this note we establish the absence of strongly RG-relevant high-gradient operators in the psl(2 vertical stroke 2) Gross-Neveu model to all loops. In addition, we determine the spectrum for a large subsector of the model at infinite coupling and observe that all scaling weights become half-integer. Evidence for a conjectured relation with the CP 1 vertical stroke 2 sigma model is not found.

  17. High-gradient operators in the psl(2|2 Gross–Neveu model

    Directory of Open Access Journals (Sweden)

    Alessandra Cagnazzo

    2015-03-01

    Full Text Available It has been observed more than 25 years ago that sigma model perturbation theory suffers from strongly RG-relevant high-gradient operators. The phenomenon was first seen in 1-loop calculations for the O(N vector model and it is known to persist at least to two loops. More recently, Ryu et al. suggested that a certain deformation of the psl(N|N WZNW-model at level k=1, or equivalently the psl(N|N  Gross–Neveu model, could be free of RG-relevant high-gradient operators and they tested their suggestion to leading order in perturbation theory. In this note we establish the absence of strongly RG-relevant high-gradient operators in the psl(2|2 Gross–Neveu model to all loops. In addition, we determine the spectrum for a large subsector of the model at infinite coupling and observe that all scaling weights become half-integer. Evidence for a conjectured relation with the CP1|2 sigma model is not found.

  18. Accoustic Localization of Breakdown in Radio Frequency Accelerating Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Peter Gwin [IIT, Chicago

    2016-07-01

    Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.

  19. radiofrequency cavity

    CERN Multimedia

    1988-01-01

    The pulse of a particle accelerator. 128 of these radio frequency cavities were positioned around CERN's 27-kilometre LEP ring to accelerate electrons and positrons. The acceleration was produced by microwave electric oscillations at 352 MHz. The electrons and positrons were grouped into bunches, like beads on a string, and the copper sphere at the top stored the microwave energy between the passage of individual bunches. This made for valuable energy savings as it reduced the heat generated in the cavity.

  20. Studies of niobium and development of niobium resonant RF cavities for accelerator driven system

    International Nuclear Information System (INIS)

    Mondal, Jayanta

    2013-01-01

    The present approach for the fabrication of superconducting radio frequency (SRF) cavities is to roll and deep draw sheets of polycrystalline high-purity niobium. Jefferson Laboratory pioneered the use of large-grain/single-crystal Nb directly sliced from an ingot for the fabrication of single-crystal high-purity Nb SRF cavities. The large grain/single crystal niobium has several potential advantages over the polycrystalline niobium and has become a viable alternative to the standard fine grain (ASTM grain size>6 μm), high purity (RRR ≥ 250 ) niobium for the fabrication of high-performance SRF cavities for particle accelerators. The present study includes the prototype single cell low beta cavity design, fabrication, EB welding and low temperature RF test at 2K. In this study also the medium field Q-Slope has been analyzed with the help of an added non linear term in Heabel's analytical model and a linear increase of surface resistance Rs with the magnetic field

  1. Baking effect on Niobium superconducting RF cavities and its physical interpretation

    Energy Technology Data Exchange (ETDEWEB)

    Saito, K. [High Energy Accelerator Research Organization, Tsukuba, Ibaraki (Japan); Kneisel, P. [Thomas Jefferson Accelerator Facility, VA, (United States)

    2000-07-01

    Recently a very surprising phenomenon has been discovered at JLab and Saclay with chemically polished niobium cavities, which the baking during vacuum evacuation has benefits to improve the cavity performance: high Q and high gradient. We have confirmed the same effect on the electropolished niobium cavities. We have analyzed the temperature dependence of the surface resistance in order to understand this effect in the frame or BCS theory. In this paper these results will be presented. (author)

  2. MECHANICAL CAVITY DESIGN FOR 100MV UPGRADE CRYOMODULE

    International Nuclear Information System (INIS)

    K.M. Wilson; G. Ciovati; E. F. Daly; J. Henry; R. Hicks; J. Hogan; D. Machie; P. Kneisel; C. Reece; J. Sekutowicz; T. Whitlatch

    2003-01-01

    To achieve up to 6 GeV, each cryomodule in the CEBAF accelerator currently provides about 30 MV of acceleration. To raise the accelerator energy to 12 GeV, ten additional cryomodules capable of providing over 100 MV of acceleration are required. A prototype of the 100 MV cryomodule has been designed, is presently under construction, and will be completed in 2004. This prototype cryomodule comprises two new cavity designs, four cavities of the low loss design and four cavities of the high gradient design. Although the cavity shapes were designed for their RF properties, the mechanical implications must be considered. In addition to the new cavity shapes, changes have also been made to the cavity end dish assemblies, weld joints, and stiffening rings. This paper will present the results of the stress and vibration analyses used for designing the cryomodule

  3. Ion Exchange Temperature Testing with SRF Resin - 12088

    Energy Technology Data Exchange (ETDEWEB)

    Russell, R.L.; Rinehart, D.E.; Brown, G.N.; Peterson, R.A. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States)

    2012-07-01

    Ion exchange using the Spherical Resorcinol-Formaldehyde (SRF) resin has been selected by the U.S. Department of Energy's Office of River Protection for use in the Pretreatment Facility of the Hanford Tank Waste Treatment and Immobilization Plant (WTP) and for potential application in an at-tank deployment for removing Cs-137. Recent proposed changes to the WTP ion exchange process baseline indicate that higher temperatures (50 deg. C) to alleviate post-filtration precipitation issues prior to reaching the ion exchange columns may be required. Therefore, it is important to understand the behavior of SRF resin performance under the conditions expected with the new equipment and process changes. This research examined the impact of elevated temperature on resin loading and resin degradation during extended solution flow at elevated temperature (45 deg., 50 deg., 55 deg., 60 deg., 65 deg., 75 deg. C). Testing for extended times at elevated temperatures showed that the resin does degrade and loading capacity is reduced at and above 45 deg. C. Above 60 deg. C the resin appears to not load at all. It was observed that the resin disintegrated at 75 deg. C until not much was left and partially disintegrated at 65 deg. C, which caused the column to plug in both tests after ∼336 hours. The results indicate that WTP will lose resin loading capacity if the ion exchange process is performed above 25 deg. C, and the resin will disintegrate above 65 deg. C. Therefore, WTP will have a restricted operating range of temperatures to perform the ion exchange process with this resin. PNNL and WTP are currently evaluating the operating limits of the resin in further detail. Aging in 0.5 M HNO{sub 3} also caused the resin to lose capacity above 25 deg. C and to completely dissolve at 55 deg. C. Again, WTP will have a restricted operating range of temperatures when eluting the resin with nitric acid in order to maintain resin loading capacity and avoid disintegration of the resin

  4. Hydroforming of Tesla Cavities at Desy

    International Nuclear Information System (INIS)

    Singer, W.; Kaiser, H.; Singer, X.; Gonin, I.; Zhelezov, I.; Khabibullin, T.; Kneisel, P.; Saito, K.

    2000-01-01

    Since several years the development of seamless niobium cavity fabrication by hydro forming is being pursued at DESY. This technique offers the possibility of lower cost of fabrication and perhaps better rf performance of the cavities because of the elimination of electron-beam welds, which in the standard fabrication technique have sometimes lead to inferior cavity performance due to defects. Several single cell 1300 MHz cavities have been formed from high purity seamless niobium tubes, which are under computer control expanded with internal pressure while simultaneously being swaged axially. The seamless tubes have been made by either back extrusion and flow forming or by spinning or deep drawing. Standard surface treatment techniques such as high temperature post purification, buffered chemical polishing (BCP), electropolishing (EP) and high pressure ultra pure water rinsing (HPR) have been applied to these cavities. The cavities exhibited high Q - values of 2 x 10 10 at 2K and residual resistances as low as 3 n(Omega) after the removal of a surface layer of app. 100 (micro)m by BCP. Surprisingly, even at high gradients up to the maximum measured values of E acc ∼ 33 MV/m the Q-value did not decrease in the absence of field emission as often observed. After electropolishing of additional 100 (micro)m one of the cavities reached an accelerating gradient of E acc (ge) 42 MV/m

  5. Test Results of the 3.9 GHz Cavity at Fermilab

    CERN Document Server

    Solyak, N

    2004-01-01

    Fermilab is developing two types of 3.9 GHz superconducting cavities to improve performances of A0 and TTF photoinjectors. In frame of this project we have built and tested two nine-cell copper models and one 3-cell niobium accelertating cavity and series of deflecting cavities. Properties of the high order modes were carefully studied in a chain of two copper cavities at room temperature. High gradient performance were tested at helium temperature. Achieved gradients and surface resistances are exceed goal parameters. In paper we discuss results of cold tests of the 3-cell accelerating and deflecting cavities.

  6. Theory of factors limiting high gradient operation of warm accelerating structures

    Energy Technology Data Exchange (ETDEWEB)

    Nusinovich, Gregory S. [Univ. of Maryland, College Park, MD (United States)

    2014-07-22

    This report consists of two parts. In the first part we describe a study of the heating of microprotrusions on surfaces of accelerating structures. This ;process is believed to lead to breakdown in these structures. Our study revealed that for current accelerator parameters melting should not occur due to space charge limitations of the current emitted by a protrusion. The second part describes a novel concept to develop THz range sources based on harmonic cyclotron masers for driving future colliders. This work was stimulated by a recent request of SLAC to develop high power, high-efficiency sources of sub-THz radiation for future high-gradient accelerators.

  7. Use of high-gradient magnetic fishing for reducing proteolysis during fermentation

    DEFF Research Database (Denmark)

    Maury, Trine Lütken; Ottow, Kim Ekelund; Brask, Jesper

    2012-01-01

    Proteolysis during fermentation may have a severe impact on the yield and quality of a secreted product. In the current study, we demonstrate the use of high-gradient magnetic fishing (HGMF) as an efficient alternative to the more conventional methods of preventing proteolytic degradation....... Bacitracin-linked magnetic affinity adsorbents were employed directly in a fermenter during Bacillus licheniformis cultivation to remove trace amounts of unwanted proteases. The constructed magnetic adsorbents had excellent, highly specific binding characteristics in the fermentation broth (K(d) = 1...

  8. Design of a High Gradient Quadrupole for the LHC Interaction Regions

    International Nuclear Information System (INIS)

    Bossert, R.; Gourlay, S.A.; Heger, T.; Huang, Y.; Kerby, J.; Lamm, M.J.; Limon, P.J.; Mazur, P.O.; Nobrega, F.; Ozelis, J.P.; Sabbi, G.; Strait, J.; Zlobin, A.V.; Caspi, S.; Dell'orco, D.; McInturff, A.D.; Scanlan, R.M.; Van Oort, J.M.; Gupta, R.C.

    1997-03-01

    A collaboration of Fermilab, Lawrence Berkeley National Laboratory and Brookhaven National Laboratory is currently engaged in the design of a high gradient quadrupole suitable for use in the LHC interaction regions. The cold iron design incorporates a two-shell, cos2θ coil geometry with a 70 mm aperture. This paper summarizes the progress on a magnetic and mechanical design that meets the requirements of maximum gradient ≥250 T/m, operation at 1.8K, high field quality and provision for adequate cooling in a high radiation environment

  9. Measurement of time dependent fields in high gradient superconducting quadrupoles for the Tevatron

    International Nuclear Information System (INIS)

    Lamm, M.J.; Coulter, K.; Gourlay, S.; Jaffery, T.S.

    1990-10-01

    Magnetic field measurements have been performed on prototype and production magnets from two high gradient superconducting quadrupoles designs. One design is a double shell quadrupole with 36 strand Rutherford cable. The other design is a single shell quadrupole with 5 individually monolithic strands connected in series. These magnets have similar bore diameters and cable dimensions. However, there are significant differences between the two designs, as well as differences between prototype and production magnets within each design, with regard to Cu to superconductor ratio, filament diameter and filament spacing to strand diameter. The time dependence of fixed currents of the measured magnetic fields is discussed. 9 refs., 6 figs., 1 tab

  10. High-gradient magnetic affinity separation of trypsin from porcine pancreatin

    DEFF Research Database (Denmark)

    Hubbuch, Jürgen; Thomas, Owen R. T.

    2002-01-01

    We introduce a robust and scale-flexible approach to macromolecule purification employing tailor-made magnetic adsorbents and high-gradient magnetic separation technology adapted from the mineral processing industries. Detailed procedures for the synthesis of large quantities of low-cost defined......-scale studies approximate to95% of the endogenous trypsin present in a crude porcine pancreatin feedstock was recovered with a purification factor of approximate to4.1 at the expense of only a 4% loss in a-amylase activity. Efficient recovery of trypsin from the same feedstock was demonstrated at a vastly...

  11. Application and Prospect of Superconducting High Gradient Magnetic Separation in Disposal of Micro-fine Tailings

    Science.gov (United States)

    Yang, Changqiao; Li, Suqin; Guo, Zijie; Kong, Jiawei

    2017-12-01

    Magnetic separation technology is playing an increasingly important role in the field of environmental protection such as waste gas, waste water and solid waste treatment. As a new type of solid waste treatment technology, superconducting high gradient magnetic separation (HGMS) is mainly applied in the separation of micro-fine weakly magnetic particles because of the advantages of high separation efficiency, energy saving, simple equipment and easy automation. In this paper, the basic principle of superconducting HGMS was firstly introduced, then the research status of scholars at home and aboard on the disposal of micro-fine tailings were summarized. Finally, the direction of development for HGMS was put forward.

  12. Development of a high gradient quadrupole for the LHC Interaction Regions

    International Nuclear Information System (INIS)

    Bossert, R.; Feher, S.; Gourlay, S.A.

    1997-04-01

    A collaboration of Fermilab, Lawrence Berkeley National Laboratory and Brookhaven National Laboratory is engaged in the design of a high gradient quadrupole suitable for use in the LHC interaction regions. The cold iron design incorporates a two-layer, cos(2θ) coil geometry with a 70 mm aperture operating in superfluid helium. This paper summarizes the progress on a magnetic, mechanical and thermal design that meets the requirements of maximum gradient above 250 T/m, high field quality and provision for adequate cooling in a high radiation environment

  13. High gradient test of the C-band choke-mode type accelerating structure

    International Nuclear Information System (INIS)

    Inagaki, T.; Shintake, T.; Baba, H.; Togawa, K.; Onoe, K.; Marechal, X.; Takashima, T.; Takahashi, S.; Matsumoto, H.

    2004-01-01

    The C-band (5712 MHz) choke-mode type accelerating structure will be used for SPring-8 Compact SASE-FEL Source (SCSS). To make the accelerator length short, we designed the field gradient as high as 40 MV/m. Since it is higher gradient than other traditional electron accelerators, we have to carefully check its performance (RF breakdown, dark current emission, etc.) in the high gradient test stand. The first experiment will be scheduled in this summer. In this paper, we will describe the preparation progress for the test. (author)

  14. High gradient experiment by accelerator test facility for Japan Linear Collider

    International Nuclear Information System (INIS)

    Takeda, Seishi; Akemoto, Mitsuo; Hayano, Hitoshi; Naito, Takashi; Matsumoto, Hiroshi

    1991-01-01

    For the e + e - linear colliders in TeV energy region such as the Japan Linear Collider (JLC), the accelerating gradient will be one of the important parameters affecting the over all design of main linacs. The gradient determines the accelerating structures, RF frequencies, peak power, AC power, total length and cost. High gradient experiment by using a traveling wave structure in S-band frequencies is presented. Discussions are given about the dependence of dark current and structure length. As one of the parameters indicating the quality of the structure, the multiplication factor η has been proposed

  15. SRF LINAC for future extension of the PEFP

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han Sung; Kwon, Hyeok Jung; Seol, Kyoung Tae; Jang, Ji Ho; Cho, Yong Sub [Proton Engineering Frontier Project, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-04-15

    A study on the superconducting RF linac is underway in order to increase the beam energy up to 1 GeV by extending the Proton Engineering Frontier Project (PEFP) 100-MeV linac. The operating frequency of the PEFP superconducting linac (SCL) is 700 MHz, which is determined by the fact that the frequency of the existing normal conducting linac is 350 MHz. A preliminary study on the beam dynamics showed that two types of cavities with geometrical betas of 0.50 and 0.74 could cover the entire energy range from 100 MeV to 1 GeV. An inductive output tube (IOT) based RF system is under consideration as a high-power RF source for the SCL due to its low operating voltage and high efficiency. As a prototyping activity for a reduced beta cavity, a five-cell cavity with a geometrical beta of 0.42 was designed and fabricated. A vertical test of the prototype cavity at low temperatures was performed to check the performance of the cavity. The design study and the prototyping activity for the PEFP SCL will be presented in this paper.

  16. SRF LINAC for future extension of the PEFP

    International Nuclear Information System (INIS)

    Kim, Han Sung; Kwon, Hyeok Jung; Seol, Kyoung Tae; Jang, Ji Ho; Cho, Yong Sub

    2014-01-01

    A study on the superconducting RF linac is underway in order to increase the beam energy up to 1 GeV by extending the Proton Engineering Frontier Project (PEFP) 100-MeV linac. The operating frequency of the PEFP superconducting linac (SCL) is 700 MHz, which is determined by the fact that the frequency of the existing normal conducting linac is 350 MHz. A preliminary study on the beam dynamics showed that two types of cavities with geometrical betas of 0.50 and 0.74 could cover the entire energy range from 100 MeV to 1 GeV. An inductive output tube (IOT) based RF system is under consideration as a high-power RF source for the SCL due to its low operating voltage and high efficiency. As a prototyping activity for a reduced beta cavity, a five-cell cavity with a geometrical beta of 0.42 was designed and fabricated. A vertical test of the prototype cavity at low temperatures was performed to check the performance of the cavity. The design study and the prototyping activity for the PEFP SCL will be presented in this paper.

  17. Fiber Optic Based Thermometry System for Superconducting RF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Kochergin, Vladimir [Microxact Inc.

    2013-05-06

    Thermometry is recognized as the best technique to identify and characterize losses in SRF cavities. The most widely used and reliable apparatus for temperature mapping at cryogenic temperatures is based on carbon resistors (RTDs). The use of this technology on multi-cell cavities is inconvenient due to the very large number of sensors required to obtain sufficient spatial resolution. Recent developments make feasible the use of multiplexible fiber optic sensors for highly distributed temperature measurements. However, sensitivity of multiplexible cryogenic temperature sensors was found extending only to 12K at best and thus was not sufficient for SRF cavity thermometry. During the course of the project the team of MicroXact, JLab and Virginia Tech developed and demonstrated the multiplexible fiber optic sensor with adequate response below 20K. The demonstrated temperature resolution is by at least a factor of 60 better than that of the best multiplexible fiber optic temperature sensors reported to date. The clear path toward at least 10times better temperature resolution is shown. The first to date temperature distribution measurements with ~2.5mm spatial resolution was done with fiber optic sensors at 2K to4K temperatures. The repeatability and accuracy of the sensors were verified only at 183K, but at this temperature both parameters significantly exceeded the state of the art. The results of this work are expected to find a wide range of applications, since the results are enabling the whole new testing capabilities, not accessible before.

  18. Statistics of vacuum breakdown in the high-gradient and low-rate regime

    Science.gov (United States)

    Wuensch, Walter; Degiovanni, Alberto; Calatroni, Sergio; Korsbäck, Anders; Djurabekova, Flyura; Rajamäki, Robin; Giner-Navarro, Jorge

    2017-01-01

    In an increasing number of high-gradient linear accelerator applications, accelerating structures must operate with both high surface electric fields and low breakdown rates. Understanding the statistical properties of breakdown occurrence in such a regime is of practical importance for optimizing accelerator conditioning and operation algorithms, as well as of interest for efforts to understand the physical processes which underlie the breakdown phenomenon. Experimental data of breakdown has been collected in two distinct high-gradient experimental set-ups: A prototype linear accelerating structure operated in the Compact Linear Collider Xbox 12 GHz test stands, and a parallel plate electrode system operated with pulsed DC in the kV range. Collected data is presented, analyzed and compared. The two systems show similar, distinctive, two-part distributions of number of pulses between breakdowns, with each part corresponding to a specific, constant event rate. The correlation between distance and number of pulses between breakdown indicates that the two parts of the distribution, and their corresponding event rates, represent independent primary and induced follow-up breakdowns. The similarity of results from pulsed DC to 12 GHz rf indicates a similar vacuum arc triggering mechanism over the range of conditions covered by the experiments.

  19. High-gradient normal-conducting RF structures for muon cooling channels

    International Nuclear Information System (INIS)

    Corlett, J.N.; Green, M.A.; Hartman, N.; Ladran, A.; Li, D.; MacGill, R.; Rimmer, R.; Moretti, A.; Jurgens, T.; Holtkamp, N.; Black, E.; Summers, D.; Booke, M.

    2001-01-01

    We present a status report on the research and development of high-gradient normal-conducting RF structures for the ionization cooling of muons in a neutrino factory or muon collider. High-gradient RF structures are required in regions enclosed in strong focusing solenoidal magnets, precluding the application of superconducting RF technology [1]. We propose using linear accelerating structures, with individual cells electromagnetically isolated, to achieve the required gradients of over 15 MV/m at 201 MHz and 30 MV/m at 805 MHz. Each cell will be powered independently, and cell length and drive phase adjusted to optimize shunt impedance of the assembled structure. This efficient design allows for relatively small field enhancement on the structure walls, and an accelerating field approximately 1.7 times greater than the peak surface field. The electromagnetic boundary of each cell may be provided by a thin Be sheet, or an assembly of thin-walled metal tubes. Use of thin, low-Z materials will allow passage of the muon beams without significant deterioration in beam quality due to scattering. R and D in design and analysis of robust structures that will operate under large electric and magnetic fields and RF current heating are discussed, including the experimental program based in a high-power test laboratory developed for this purpose

  20. Statistics of vacuum breakdown in the high-gradient and low-rate regime

    Directory of Open Access Journals (Sweden)

    Walter Wuensch

    2017-01-01

    Full Text Available In an increasing number of high-gradient linear accelerator applications, accelerating structures must operate with both high surface electric fields and low breakdown rates. Understanding the statistical properties of breakdown occurrence in such a regime is of practical importance for optimizing accelerator conditioning and operation algorithms, as well as of interest for efforts to understand the physical processes which underlie the breakdown phenomenon. Experimental data of breakdown has been collected in two distinct high-gradient experimental set-ups: A prototype linear accelerating structure operated in the Compact Linear Collider Xbox 12 GHz test stands, and a parallel plate electrode system operated with pulsed DC in the kV range. Collected data is presented, analyzed and compared. The two systems show similar, distinctive, two-part distributions of number of pulses between breakdowns, with each part corresponding to a specific, constant event rate. The correlation between distance and number of pulses between breakdown indicates that the two parts of the distribution, and their corresponding event rates, represent independent primary and induced follow-up breakdowns. The similarity of results from pulsed DC to 12 GHz rf indicates a similar vacuum arc triggering mechanism over the range of conditions covered by the experiments.

  1. Cryogenic testing of the 2.1 GHz five-cell superconducting RF cavity with a photonic band gap coupler cell

    Science.gov (United States)

    Arsenyev, Sergey A.; Temkin, Richard J.; Haynes, W. Brian; Shchegolkov, Dmitry Yu.; Simakov, Evgenya I.; Tajima, Tsuyoshi; Boulware, Chase H.; Grimm, Terrence L.; Rogacki, Adam R.

    2016-05-01

    We present results from cryogenic tests of the multi-cell superconducting radio frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving high average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery-linacs (ERLs). Beam current in ERLs is limited by the beam break-up instability, caused by parasitic higher order modes (HOMs) interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The multi-cell cavity was designed and fabricated of niobium. Two cryogenic (vertical) tests were conducted. The high unloaded Q-factor was demonstrated at a temperature of 4.2 K at accelerating gradients up to 3 MV/m. The measured value of the unloaded Q-factor was 1.55 × 108, in agreement with prediction.

  2. CEBAF SRF Performance during Initial 12 GeV Commissioning

    International Nuclear Information System (INIS)

    Bachimanchi, Ramakrishna; Allison, Trent; Daly, Edward; Drury, Michael; Hovater, J; Lahti, George; Mounts, Clyde; Nelson, Richard; Plawski, Tomasz

    2015-09-01

    The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of eleven new 100 MV cryomodules (88 cavities). The superconducting RF cavities are designed to operate CW at an accelerating gradient of 19.3 MV/m with a Q L of 3x10 7 . Not all the cavities were operated at the minimum gradient of 19.3 MV/m with the beam. Though the initial 12 GeV milestones were achieved during the initial commissioning of CEBAF, there are still some issues to be addressed for long term reliable operation of these modules. This paper reports the operational experiences during the initial commissioning and the path forward to improve the performance of C100 (100 MV) modules.

  3. Thermal design studies in superconducting rf cavities: Phonon peak and Kapitza conductance

    Directory of Open Access Journals (Sweden)

    A. Aizaz

    2010-09-01

    Full Text Available Thermal design studies of superconducting radio frequency (SRF cavities involve two thermal parameters, namely the temperature dependent thermal conductivity of Nb at low temperatures and the heat transfer coefficient at the Nb-He II interface, commonly known as the Kapitza conductance. During the fabrication process of the SRF cavities, Nb sheet is plastically deformed through a deep drawing process to obtain the desired shape. The effect of plastic deformation on low temperature thermal conductivity as well as Kapitza conductance has been studied experimentally. Strain induced during the plastic deformation process reduces the thermal conductivity in its phonon transmission regime (disappearance of phonon peak by 80%, which may explain the performance limitations of the defect-free SRF cavities during their high field operations. Low temperature annealing of the deformed Nb sample could not recover the phonon peak. However, moderate temperature annealing during the titanification process recovered the phonon peak in the thermal conductivity curve. Kapitza conductance measurements for the Nb-He II interface for various surface topologies have also been carried out before and after the annealing. These measurements reveal consistently increased Kapitza conductance after the annealing process was carried out in the two temperature regimes.

  4. A compact high-gradient 25 MeV 17 GHz RF linac for free-electron laser research

    International Nuclear Information System (INIS)

    Danly, B.G.; Chen, S.C.; Kreischer, K.E.

    1995-01-01

    A new compact high-gradient (60 MeV/m) high-frequency (17.136 GHz) RF linac is presently under construction by Haimson Research Corp. (HRC) for installation at the MIT Plasma Fusion Center in the High-Gradient Accelerator and High Power Microwave Laboratory. This accelerator will utilize an existing traveling-wave relativistic klystron (TWRK) which is now operation at MIT with 25 MW power, 67 dB gain, and 52% efficiency at 17.136 GHz

  5. Researches on bake effect on RF superconducting cavities

    International Nuclear Information System (INIS)

    Hao Jiankui; Zhao Kui; Zhu Feng

    2005-01-01

    The Q-slope at high gradient affects the performance of superconducting cavity greatly. Recent researches show that low temperature (100-150) degree C heat treatment (bake) has positive effects on the performance of superconducting cavities. A lot of cavity tests are analyzed based on bake treatment. The average gradient E acc,max and E acc at Q=1 x 10 10 are increased by more than 3.5 MV/m. Q at E acc,max is increased and the Q-slope is improved. Analysis on bake temperature shows that higher bake temperature leads to higher Q value. Comparison of BCP and EP cavities shows that at least 60-80 μm EP is needed for BCP surface. More than 10-15 μm removal of the surface by BCP will degrade the performance of an EP cavity. Oxygen diffusion model is used to illustrate bake effect. (authors)

  6. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Shahid, E-mail: shahid.ahmed@ieee.org [BML Munjal University, Gurgaon, Haryana 123413 (India); Mammosser, John D. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-07-15

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O{sub 2} (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM{sub 010}-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  7. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    Science.gov (United States)

    Ahmed, Shahid; Mammosser, John D.

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  8. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    International Nuclear Information System (INIS)

    Ahmed, Shahid; Mammosser, John D.

    2015-01-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O 2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM 010 -mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper

  9. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity.

    Science.gov (United States)

    Ahmed, Shahid; Mammosser, John D

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  10. Design and performance of a new induction furnace for heat treatment of superconducting radiofrequency niobium cavities.

    Science.gov (United States)

    Dhakal, Pashupati; Ciovati, Gianluigi; Rigby, Wayne; Wallace, John; Myneni, Ganapati Rao

    2012-06-01

    Superconducting radio frequency (SRF) cavities made of high purity niobium (Nb) are the building blocks of many modern particle accelerators. The fabrication process includes several cycles of chemical and heat treatment at low (∼120 °C) and high (∼800 °C) temperatures. In this contribution, we describe the design and performance of an ultra-high-vacuum furnace which uses an induction heating system to heat treat SRF cavities. Cavities are heated by radiation from the Nb susceptor. By using an all-niobium hot zone, contamination of the Nb cavity by foreign elements during heat treatment is minimized and allows avoiding subsequent chemical etching. The furnace was operated up to 1400 °C with a maximum pressure of ∼1 × 10(-5) Torr and the maximum achievable temperature is estimated to be higher than 2000 °C. Initial results on the performance of a single cell 1.5 GHz cavity made of ingot Nb heat treated at 1200 °C using this new induction furnace and without subsequent chemical etching showed a reduction of the RF losses by a factor of ∼2 compared to cavities made of fine-grain Nb which underwent standard chemical and heat treatments.

  11. Development of high pressure rinsing set up for 650 MHz, 5- cell superconducting RF cavity cleaning

    International Nuclear Information System (INIS)

    Suhane, S.K.; Chauhan, S.K.; Bose, A.; Kokil, S.V.; Rajput, D.S.; Oraon, B.; Md Hussain; Sahu, A.; Raghavendra, S.; Joshi, S.C.

    2015-01-01

    High pressure rinsing (HPR) is an ultra-cleanliness process for the surface preparation of high field superconducting RF cavities. Any dust particle or chemical residue on the interior of cavity causes field emission. Jets of high pressure (80-100 bar) ultra pure water dislodge surface contaminants that normally resist removal with conventional rinsing procedures, leading to substantial reduction in field emission and better cavity performance. For cleaning of 650 MHz, 5-cell SRF cavities, a high pressure rinsing set up has been developed at RRCAT. The HPR tool has a rotating wand coaxial with the vertically mounted SRF cavity that is moving up and down. Fan style spray nozzles are attached to the end of the rotating wand and the water jets emerging from spray nozzles scan the entire internal surface of the cavity. The set-up was installed in a specially built clean area meeting cleanliness class 100 standards. The ultrapure water with resistivity 2 ≥ 18 MΩ-cm required for rinsing is obtained from a dedicated water purification system installed for this purpose. The paper describes the salient design and constructional details of the high pressure rinsing set up. Characterization of water jet parameters based on the momentum transfer between the water jet and a load cell is also presented. (author)

  12. Ka-Band Rf Transmission Line Components for a High-Gradient Linear Accelerator. Final report

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2005-01-01

    High-power, high-vacuum prototypes of a variety of components for use at 34 GHz were developed. These include waveguide tapers, right-angle miter bends, windows, mode converters, power combiners, mode launchers, phase shifters, dual directional couplers, and loads. High-power, high-vacuum prototypes of all the components were built and tested up to 45 MW, using the Omega-P 34-GHz magnicon. Peak power limits for the components were determined using a quasi-optical rf pulse compressor, developed under a companion project. The components and the magnicon were configured into a user's facility for research and development by others on high-gradient accelerator structures for a future high-energy electron-positron collider.

  13. The chirped-pulse inverse free-electron laser: A high-gradient vacuum laser accelerator

    International Nuclear Information System (INIS)

    Hartemann, F.V.; Landahl, E.C.; Troha, A.L.; Van Meter, J.R.; Baldis, H.A.; Freeman, R.R.; Luhmann, N.C. Jr.; Song, L.; Kerman, A.K.; Yu, D.U.

    1999-01-01

    The inverse free-electron laser (IFEL) interaction is studied theoretically and computationally in the case where the drive laser intensity approaches the relativistic regime, and the pulse duration is only a few optical cycles long. The IFEL concept has been demonstrated as a viable vacuum laser acceleration process; it is shown here that by using an ultrashort, ultrahigh-intensity drive laser pulse, the IFEL interaction bandwidth and accelerating gradient are increased considerably, thus yielding large energy gains. Using a chirped pulse and negative dispersion focusing optics allows one to take further advantage of the laser optical bandwidth and produce a chromatic line focus maximizing the gradient. The combination of these novel ideas results in a compact vacuum laser accelerator capable of accelerating picosecond electron bunches with a high gradient (GeV/m) and very low energy spread. copyright 1999 American Institute of Physics

  14. How a High-Gradient Magnetic Field Could Affect Cell Life

    Science.gov (United States)

    Zablotskii, Vitalii; Polyakova, Tatyana; Lunov, Oleg; Dejneka, Alexandr

    2016-01-01

    The biological effects of high-gradient magnetic fields (HGMFs) have steadily gained the increased attention of researchers from different disciplines, such as cell biology, cell therapy, targeted stem cell delivery and nanomedicine. We present a theoretical framework towards a fundamental understanding of the effects of HGMFs on intracellular processes, highlighting new directions for the study of living cell machinery: changing the probability of ion-channel on/off switching events by membrane magneto-mechanical stress, suppression of cell growth by magnetic pressure, magnetically induced cell division and cell reprograming, and forced migration of membrane receptor proteins. By deriving a generalized form for the Nernst equation, we find that a relatively small magnetic field (approximately 1 T) with a large gradient (up to 1 GT/m) can significantly change the membrane potential of the cell and thus have a significant impact on not only the properties and biological functionality of cells but also cell fate. PMID:27857227

  15. Fabrication Technologies of the High Gradient Accelerator Structures at 100MV/m Range

    CERN Document Server

    Wang, Juwen; Van Pelt, John; Yoneda, Charles; Gudkov, D; Riddone, Germana; Higo, Toshiyasu; Takatomi, Toshikazu

    2010-01-01

    A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of <5×10-7/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed

  16. Recent development of high gradient superconducting magnetic separator for kaolin in China

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zian; Wang, Meifen; Ning, Fei Peng; Yang, Huan; Zhang, Guoqing; Hou, Zhi Long; Liu, Zhaong Xiu; Dai, Zhong [Institute of High Energy Physics and University of Chinese Academy of Sciences, Beijing (China); Li, Pei Yong; Zhang, Yiting; Wang, Zhaolian [Weifang Xinli Superconducting Technology Co.,Ltd., Weifang (China)

    2017-03-15

    A series of high gradient superconducting magnetic separator (HGMS) for kaolin has been developed. It is used for processing kaolin to increase the brightness or whiteness whether it is for paper or ceramic applications. The HGMS system mainly consists of a solenoid magnet with a zero boil-off helium cryostat, a double reciprocating canisters system, and a PLC (Process Logic Controller) fully automatic control system based on SCADA (Supervisory Control and Data Acquisition) system. We have successfully developed CGC-5.5/300 and CGC-5.0/500 HGMS systems in the recent years, and now three sets of them are on-site operation in different customers. This paper will present recent progress of the HGMS system, the results of some experiments on processing kaolin clay used HGMS, and the on-site operation.

  17. Characteristics of high gradient insulators for accelerator and high power flow applications

    International Nuclear Information System (INIS)

    Elizondo, J.M.; Krogh, M.L.; Smith, D.

    1997-07-01

    The high gradient insulator has been demonstrated to operate at levels comparable or better than special geometry or coated insulators. Some patented insulator configurations allow for sophisticated accelerator structures, high power flow interfaces, and microwave applications not previously possible. Sophisticated manufacturing techniques available at AlliedSignal FM and T made this development possible. Bipolar and high power flow applications are specially suited for present insulator designs. The insulator shows a beneficial effect when used under RF fields or RF structures. These insulators can be designed, to a first approximation, from simple electron flight path equations. With a recently developed model of surface flashover physics the authors completed a set of design calculations that include effects such as layer density and dielectric/metal thickness. Experimental data, obtained in the last few years of development, is presented and reviewed. Several insulator fabrication characteristics, indicating critical design parameters, are also presented

  18. Recent development of high gradient superconducting magnetic separator for kaolin in China

    International Nuclear Information System (INIS)

    Zhu, Zian; Wang, Meifen; Ning, Fei Peng; Yang, Huan; Zhang, Guoqing; Hou, Zhi Long; Liu, Zhaong Xiu; Dai, Zhong; Li, Pei Yong; Zhang, Yiting; Wang, Zhaolian

    2017-01-01

    A series of high gradient superconducting magnetic separator (HGMS) for kaolin has been developed. It is used for processing kaolin to increase the brightness or whiteness whether it is for paper or ceramic applications. The HGMS system mainly consists of a solenoid magnet with a zero boil-off helium cryostat, a double reciprocating canisters system, and a PLC (Process Logic Controller) fully automatic control system based on SCADA (Supervisory Control and Data Acquisition) system. We have successfully developed CGC-5.5/300 and CGC-5.0/500 HGMS systems in the recent years, and now three sets of them are on-site operation in different customers. This paper will present recent progress of the HGMS system, the results of some experiments on processing kaolin clay used HGMS, and the on-site operation

  19. Free-electron laser as a power source for a high-gradient accelerating structure

    International Nuclear Information System (INIS)

    Sessler, A.M.

    1982-02-01

    A two beam colliding linac accelerator is proposed in which one beam is intense (approx. = 1KA), of low energy (approx. = MeV), and long (approx. = 100 ns) and provides power at 1 cm wavelength through a free-electron-laser-mechanism to the second beam of a few electrons (approx. = 10 11 ), which gain energy at the rate of 250 MeV/m in a high-gradient accelerating structure and hence reach 375 GeV in 1.5 km. The intense beam is given energy by induction units and gains, and losses by radiation, 250 keV/m thus supplying 25 J/m to the accelerating structure. The luminosity, L, of two such linacs would be, at a repetition rate of 1 kHz, L = 4. x 10 32 cm -2 s -1

  20. HIGH-GRADIENT, HIGH-TRANSFORMER-RATIO, DIELECTRIC WAKE FIELD ACCELERATOR

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2012-04-12

    The Phase I work reported here responds to DoE'ss stated need "...to develop improved accelerator designs that can provide very high gradient (>200 MV/m for electrons...) acceleration of intense bunches of particles." Omega-P's approach to this goal is through use of a ramped train of annular electron bunches to drive a coaxial dielectric wakefield accelerator (CDWA) structure. This approach is a direct extension of the CDWA concept from acceleration in wake fields caused by a single drive bunch, to the more efficient acceleration that we predict can be realized from a tailored (or ramped) train of several drive bunches. This is possible because of a much higher transformer ratio for the latter. The CDWA structure itself has a number of unique features, including: a high accelerating gradient G, potentially with G > 1 GeV/m; continuous energy coupling from drive to test bunches without transfer structures; inherent transverse focusing forces for particles in the accelerated bunch; highly stable motion of high charge annular drive bunches; acceptable alignment tolerances for a multi-section system. What is new in the present approach is that the coaxial dielectric structure is now to be energized by-not one-but by a short train of ramped annular-shaped drive bunches moving in the outer coaxial channel of the structure. We have shown that this allows acceleration of an electron bunch traveling along the axis in the inner channel with a markedly higher transformer ratio T than for a single drive bunch. As described in this report, the structure will be a GHz-scale prototype with cm-scale transverse dimensions that is expected to confirm principles that can be applied to the design of a future THz-scale high gradient (> 500 MV/m) accelerator with mm-scale transverse dimensions. We show here a new means to significantly increase the transformer ratio T of the device, and thereby to significantly improve its suitability as a flexible and effective component in

  1. How a High-Gradient Magnetic Field Could Affect Cell Life

    Science.gov (United States)

    Zablotskii, Vitalii; Polyakova, Tatyana; Lunov, Oleg; Dejneka, Alexandr

    2016-11-01

    The biological effects of high-gradient magnetic fields (HGMFs) have steadily gained the increased attention of researchers from different disciplines, such as cell biology, cell therapy, targeted stem cell delivery and nanomedicine. We present a theoretical framework towards a fundamental understanding of the effects of HGMFs on intracellular processes, highlighting new directions for the study of living cell machinery: changing the probability of ion-channel on/off switching events by membrane magneto-mechanical stress, suppression of cell growth by magnetic pressure, magnetically induced cell division and cell reprograming, and forced migration of membrane receptor proteins. By deriving a generalized form for the Nernst equation, we find that a relatively small magnetic field (approximately 1 T) with a large gradient (up to 1 GT/m) can significantly change the membrane potential of the cell and thus have a significant impact on not only the properties and biological functionality of cells but also cell fate.

  2. Possible role of rf melted microparticles on the operation of high-gradient accelerating structures

    Directory of Open Access Journals (Sweden)

    G. S. Nusinovich

    2009-10-01

    Full Text Available High-gradient accelerating structures should operate reliably for a long time. Therefore studies of various processes which may lead to disruption of such an operation are so important. In the present paper, the dissipation of rf electromagnetic energy in metallic microparticles is analyzed accounting for the temperature dependence of the skin depth. Such particles may appear in structures, for example, due to mechanical fracture of irises in strong rf electric fields. It is shown that such microparticles with dimensions on the order of the skin depth, being immersed in the region of strong rf magnetic field, can absorb enough energy in long-pulse operation to be melted. Then, the melted clumps can impinge on the surface of a structure and create nonuniformities leading to field enhancement and corresponding emission of dark current. Results are given for several geometries and materials of microparticles.

  3. Phase and Frequency Locked Magnetrons for SRF Sources

    Energy Technology Data Exchange (ETDEWEB)

    Neubauer, Michael [Muons, Inc.; Johnson, Rolland

    2014-09-12

    There is great potential for a magnetron power source that can be controlled both in phase and frequency. Such a power source could revolutionize many particle accelerator systems that require lower capital cost and/or higher power efficiency. Beyond the accelerator community, phase and frequency locked magnetons could improve radar systems around the world and make affordable phased arrays for wireless power transmission for solar powered satellites. This joint project of Muons, Inc., Fermilab, and L-3 CTL was supported by an STTR grant monitored by the Nuclear Physics Office of the DOE Office of Science. The object of the program was to incorporate ferrite materials into the anode of a magnetron and, with appropriate biasing of the ferrites, to maintain frequency lock and to allow for frequency adjustment of the magnetron without mechanical tuners. If successful, this device would have a dual use both as a source for SRF linacs and for military applications where fast tuning of the frequency is a requirement. In order to place the materials in the proper location, several attributes needed to be modeled. First the impact of the magnetron’s magnetic field needed to be shielded from the ferrites so that they were not saturated. And second, the magnetic field required to change the frequency of the magnetron at the ferrites needed to be shielded from the region containing the circulating electrons. ANSYS calculations of the magnetic field were used to optimize both of these parameters. Once the design for these elements was concluded, parts were fabricated and a complete test assembly built to confirm the predictions of the computer models. The ferrite material was also tested to determine its compatibility with magnetron tube processing temperatures. This required a vacuum bake out of the chosen material to determine the cleanliness of the material in terms of outgassing characteristics, and a subsequent room temperature test to verify that the characteristics of

  4. Influence of SrF_2-doping in AlN ceramics on scintillation and dosimeter properties

    International Nuclear Information System (INIS)

    Kojima, Kaori; Okada, Go; Fukuda, Kentaro; Yanagida, Takayuki

    2016-01-01

    In this study, we synthesized undoped AlN and SrF_2-doped AlN (AlN-SrF_2) ceramics by Spark Plasma Sintering (SPS), and we characterized their optical, scintillation and dosimeter properties. The prepared undoped AlN ceramic had gray color and visually non-transparent whereas, with an addition of SrF_2, the transparency improved and became translucent. The measured in-line transmittance was approximately 0.2% at wavelengths longer than 500 nm. While the addition of SrF_2 decreased the scintillation intensity, the decay time was significantly fastened, which is a great advantage for fast photon counting-based measurements. Both the thermally-stimulated luminescence (TSL) and optically-stimulated luminescence (OSL) showed good linear response from the milli-gray range to over 10 Gy. The sensitivity seems to decrease by an addition of SrF_2 as it suppresses structural defect centers which are responsible for dosimeter properties. However, the main TSL glow peak position shifts to higher temperature with the addition of SrF_2, which indicates that inclusion of SrF_2 improves the TSL signal stability. - Highlights: • We synthesized undoped and SrF_2-doped AlN ceramics by Spark Plasma Sintering. • We evaluated scintillator and dosimeter properties of undoped and SrF_2-doped AlN. • By doping with SrF_2, the decay time is shortened. • By doping with SrF_2, the stability of TSL and OSL is improved.

  5. Rf transfer in the Coupled-Cavity Free-Electron Laser Two-Beam Accelerator

    International Nuclear Information System (INIS)

    Makowski, M.A.

    1991-01-01

    A significant technical problem associated with the Coupled-Cavity Free-Electron Laser Two-Beam Accelerator is the transfer of RF energy from the drive accelerator to the high-gradient accelerator. Several concepts have been advanced to solve this problem. This paper examines one possible solution in which the drive and high-gradient cavities are directly coupled to one another by means of holes in the cavity walls or coupled indirectly through a third intermediate transfer cavity. Energy cascades through the cavities on a beat frequency time scale which must be made small compared to the cavity skin time but large compared to the FEL pulse length. The transfer is complicated by the fact that each of the cavities in the system can support many resonant modes near the chosen frequency of operation. A generalized set of coupled-cavity equations has been developed to model the energy transfer between the various modes in each of the cavities. For a two cavity case transfer efficiencies in excess of 95% can be achieved. 3 refs., 2 figs

  6. Multi-Mode Cavity Accelerator Structure

    International Nuclear Information System (INIS)

    Jiang, Yong; Hirshfield, Jay Leonard

    2016-01-01

    This project aimed to develop a prototype for a novel accelerator structure comprising coupled cavities that are tuned to support modes with harmonically-related eigenfrequencies, with the goal of reaching an acceleration gradient >200 MeV/m and a breakdown rate <10"-"7/pulse/meter. Phase I involved computations, design, and preliminary engineering of a prototype multi-harmonic cavity accelerator structure; plus tests of a bimodal cavity. A computational procedure was used to design an optimized profile for a bimodal cavity with high shunt impedance and low surface fields to maximize the reduction in temperature rise Δ T. This cavity supports the TM010 mode and its 2nd harmonic TM011 mode. Its fundamental frequency is at 12 GHz, to benchmark against the empirical criteria proposed within the worldwide High Gradient collaboration for X-band copper structures; namely, a surface electric field E_s_u_r"m"a"x< 260 MV/m and pulsed surface heating Δ T"m"a"x< 56 °K. With optimized geometry, amplitude and relative phase of the two modes, reductions are found in surface pulsed heating, modified Poynting vector, and total RF power - as compared with operation at the same acceleration gradient using only the fundamental mode.

  7. Multi-Mode Cavity Accelerator Structure

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yong [Yale Univ., New Haven, CT (United States); Hirshfield, Jay Leonard [Omega-P R& D, Inc., New Haven, CT (United States)

    2016-11-10

    This project aimed to develop a prototype for a novel accelerator structure comprising coupled cavities that are tuned to support modes with harmonically-related eigenfrequencies, with the goal of reaching an acceleration gradient >200 MeV/m and a breakdown rate <10-7/pulse/meter. Phase I involved computations, design, and preliminary engineering of a prototype multi-harmonic cavity accelerator structure; plus tests of a bimodal cavity. A computational procedure was used to design an optimized profile for a bimodal cavity with high shunt impedance and low surface fields to maximize the reduction in temperature rise ΔT. This cavity supports the TM010 mode and its 2nd harmonic TM011 mode. Its fundamental frequency is at 12 GHz, to benchmark against the empirical criteria proposed within the worldwide High Gradient collaboration for X-band copper structures; namely, a surface electric field Esurmax< 260 MV/m and pulsed surface heating ΔTmax< 56 °K. With optimized geometry, amplitude and relative phase of the two modes, reductions are found in surface pulsed heating, modified Poynting vector, and total RF power—as compared with operation at the same acceleration gradient using only the fundamental mode.

  8. The interaction between a beam and a superconducting cavity module: Measurements in CESR and CESR-Phase 3 goals

    Energy Technology Data Exchange (ETDEWEB)

    Belomestnykh, S; Flynn, G; Hartung, W; Kirchgessner, J; Moffat, D; Muller, H; Padamsee, H; Pisharody, M; Veshcherevich, V [Cornell Univ., Ithaca, NY (United States). Lab. of Nuclear Studies

    1996-08-01

    Plans for the next generation of electron-positron colliders (B-factories and B-factory-like machines) call for high beam currents to produce luminosities of the order of 10 (exp 33). To store these high currents in a machine, special attention must be paied to the interaction of the beam with discontinuities in the surrounding vacuum chamber. RF cavities are among the biggest perturbations in accelerator vacuum chambers and are therefore among the biggest sources of beam instabilities. Accelerating structures of new machines are being designed to have smaller impedance to reduce the beam-cavity interaction. Prototypes for the cavity, input coupler, cryostat, and higher-order mode (HOM) loads were subjected and are tested in CESR. A superconducting (SRF) cavity was installed in addition to the four five-cell normal conducting cavities. As a result, the calorimetry and RF power results agree with predictions up to their respective uncertainties. The results of wake potential sampling suggested that the wake fields of the SRF cavity will not limit the performance of CESR in bunch train operation. No beam instabilities or dangerous HOMs were encountered while sweeping the HOM frequencies using the cavity tuner or while exciting multipole HOMs by displacing the beam off axis. (G.K.)

  9. Distribution, behavior, and transport of inorganic and methylmercury in a high gradient stream

    International Nuclear Information System (INIS)

    Flanders, J.R.; Turner, R.R.; Morrison, T.; Jensen, R.; Pizzuto, J.; Skalak, K.; Stahl, R.

    2010-01-01

    Research highlights: → Sources of inorganic mercury widespread in high-gradient fluvial system decades after mercury use ceased in watershed. → Soils release more inorganic mercury than sediment, primarily complexed by colloids. → Methylmercury is produced in wide range of habitats despite the high gradient and coarse-grained nature of river. → Methylmercury under complex physical and chemical controls, including temperature, bioavailable mercury, and substrates (carbon and electron acceptors). - Abstract: Concentrations of Hg remain elevated in physical and biological media of the South River (Virginia, USA), despite the cessation of the industrial use of Hg in its watershed nearly six decades ago, and physical characteristics that would not seem to favor Hg(II)-methylation. A 3-a study of inorganic Hg (IHg) and methylmercury (MeHg) was conducted in physical media (soil, sediment, surface water, porewater and soil/sediment extracts) to identify non-point sources, transport mechanisms, and potential controls on Hg(II)-methylation. Data collected from surface water and sediment indicate that the majority of the non-point sources of IHg to the South River are within the first 14 km downstream from the historic point source. Partitioning data indicate that particle bound IHg is introduced in this reach, releasing dissolved and colloidal bound IHg, which is transported downstream. Extraction experiments revealed that floodplain soils released a higher fraction of their IHg content in aqueous extractions than fine-grained sediment (FGS). Based on ultrafiltration [<5000 nominal molecular weight cutoff (NMWC)] the majority of soil IHg released was colloidal in nature, providing evidence for the continued evolution of IHg for Hg(II)-methylation from soil. Strong seasonal patterns in MeHg concentrations were observed in surface water and sediment. The highest concentrations of MeHg in surface water were observed at moderate temperatures, suggesting that other

  10. Distribution, behavior, and transport of inorganic and methylmercury in a high gradient stream

    Energy Technology Data Exchange (ETDEWEB)

    Flanders, J.R., E-mail: john_flanders@urscorp.com [URS Corporation, 335 Commerce Drive, Suite 300, Fort Washington, PA 19034 (United States); Turner, R.R. [RTGeosciences Inc., PO Box 421, Squamish, BC (Canada); Morrison, T. [URS Corporation, 335 Commerce Drive, Suite 300, Fort Washington, PA 19034 (United States); Jensen, R. [Unique Environmental Services, 5406 Crestline Rd., Wilmington, DE 19808 (United States); Pizzuto, J. [University of Delaware, Department of Geology, 101D Penny Hall, Newark, DE 19716 (United States); Skalak, K. [US Geological Survey, 430 National Center, Reston, VA 20192 (United States); Stahl, R. [DuPont Corporate Remediation Group, 1447 Lancaster Pike, Wilmington, DE (United States)

    2010-11-15

    Research highlights: {yields} Sources of inorganic mercury widespread in high-gradient fluvial system decades after mercury use ceased in watershed. {yields} Soils release more inorganic mercury than sediment, primarily complexed by colloids. {yields} Methylmercury is produced in wide range of habitats despite the high gradient and coarse-grained nature of river. {yields} Methylmercury under complex physical and chemical controls, including temperature, bioavailable mercury, and substrates (carbon and electron acceptors). - Abstract: Concentrations of Hg remain elevated in physical and biological media of the South River (Virginia, USA), despite the cessation of the industrial use of Hg in its watershed nearly six decades ago, and physical characteristics that would not seem to favor Hg(II)-methylation. A 3-a study of inorganic Hg (IHg) and methylmercury (MeHg) was conducted in physical media (soil, sediment, surface water, porewater and soil/sediment extracts) to identify non-point sources, transport mechanisms, and potential controls on Hg(II)-methylation. Data collected from surface water and sediment indicate that the majority of the non-point sources of IHg to the South River are within the first 14 km downstream from the historic point source. Partitioning data indicate that particle bound IHg is introduced in this reach, releasing dissolved and colloidal bound IHg, which is transported downstream. Extraction experiments revealed that floodplain soils released a higher fraction of their IHg content in aqueous extractions than fine-grained sediment (FGS). Based on ultrafiltration [<5000 nominal molecular weight cutoff (NMWC)] the majority of soil IHg released was colloidal in nature, providing evidence for the continued evolution of IHg for Hg(II)-methylation from soil. Strong seasonal patterns in MeHg concentrations were observed in surface water and sediment. The highest concentrations of MeHg in surface water were observed at moderate temperatures

  11. Potential uses of high gradient magnetic filtration for high-temperature water purification in boiling water reactors

    International Nuclear Information System (INIS)

    Elliott, H.H.; Holloway, J.H.; Abbott, D.G.

    1979-01-01

    Studies of various high-temperature filter devices indicate a potentially positive impact for high gradient magnetic filtration on boiling water reactor radiation level reduction. Test results on in-plant water composition and impurity crystallography are presented for several typical boiling water reactors (BWRs) on plant streams where high-temperature filtration may be particularly beneficial. An experimental model on the removal of red iron oxide (hematite) from simulated reactor water with a high gradient magnetic filter is presented, as well as the scale-up parameters used to predict the filtration efficiency on various high temperature, in-plant streams. Numerical examples are given to illustrate the crud removal potential of high gradient magnetic filters installed at alternative stream locations under typical, steady-state, plant operating conditions

  12. Toward industrialization: Supporting the manufacturing processes of superconducting cavities at DESY

    International Nuclear Information System (INIS)

    Buerger, J.; Dammann, J.A.; Hagge, L.; Iversen, J.; Matheisen, A.; Singer, W.

    2006-01-01

    Manufacturing high-gradient superconducting cavities for future accelerators requires detailed knowledge of the entire production process. This knowledge has to be transferred from the laboratories, which are developing the process, to industry in order to achieve reproducible results in the industrial production of large numbers of cavities. The paper introduces DESY's approach to process industrialization based on the use of an engineering data management system (EDMS)

  13. Phase and Frequency Locked Magnetrons for SRF Sources

    International Nuclear Information System (INIS)

    Neubauer, M.; Johnson, R.P.; Popovic, M.; Moretti, A.

    2009-01-01

    Magnetrons are low-cost highly-efficient microwave sources, but they have several limitations, primarily centered about the phase and frequency stability of their output. When the stability requirements are low, such as for medical accelerators or kitchen ovens, magnetrons are the very efficient power source of choice. But for high energy accelerators, because of the need for frequency and phase stability - proton accelerators need 1-2 degrees source phase stability, and electron accelerators need .1-.2 degrees of phase stability - they have rarely been used. We describe a novel variable frequency cavity technique which will be utilized to phase and frequency lock magnetrons.

  14. High Gradient Performance of NLC/GLC X-Band Accelerating Structures

    CERN Document Server

    Döbert, Steffen; Boffo, Cristian; Bowden, Gordon B; Burke, David; Carter, Harry; Chan, Jose; Dolgashev, Valery A; Frisch, Josef; Funahashi, Y; Gonin, Ivan V; Hayano, Hitoshi; Higashi, Norio; Higashi, Yasuo; Higo, Toshiyasu; Jobe, R Keith; Jones, Roger M; Kawamata, H; Khabiboulline, Timergali N; Kirby, Robert; Kume, T; Lewandowski, James R; Li, Zenghai; McCormick, Douglas; Miller, Roger H; Mishra, Shekhar; Morozumi, Yuichi; Nantista, Christopher D; Nelson, Janice; Pearson, Chris; Romanov, Gennady; Ross, Marc; Schultz, David; Smith, Tonee; Solyak, Nikolay; Tacku Arkan, Tug; Takata, Koji; Takatomi, Toshikazu; Tantawi, Sami G; Toge, Nobu; Ueno, K; Wang, Juwen W; Watanabe, Y

    2005-01-01

    During the past five years, there has been an concerted effort at FNAL, KEK and SLAC to develop accelerator structures that meet the high gradient performance requirements for the Next Linear Collider (NLC) and Global Linear Collider (GLC) initiatives. The structure that resulted is a 60-cm-long, traveling-wave design with low group velocity (< 4% c) and a 150 degree phase advance per cell. It has an average iris size that produces an acceptable short-range wakefield in the linacs, and dipole mode damping and detuning that adequately suppresses the long-range wakefield. More than eight such structures have operated over 1000 hours at a 60 Hz pulse rate at the design gradient (65 MV/m) and pulse length (400 ns), and have reached breakdown rate levels below the limit for the linear collider. Moreover, the structures are robust in that the breakdown rates continue to decrease over time, and if the structures are briefly exposed to air, the rates recover to their low values within a few days. This paper pr...

  15. Adsorption combined with superconducting high gradient magnetic separation technique used for removal of arsenic and antimony.

    Science.gov (United States)

    Qi, Zenglu; Joshi, Tista Prasai; Liu, Ruiping; Li, Yiran; Liu, Huijuan; Qu, Jiuhui

    2018-02-05

    Manganese iron oxide (MnFe 2 O 4 ), an excellent arsenic(As)/antimony(Sb) removal adsorbent, is greatly restricted for the solid-liquid separation. Through the application of superconducting high gradient magnetic separation (HGMS) technique, we herein constructed a facility for the in situ solid-liquid separation of micro-sized MnFe 2 O 4 adsorbent in As/Sb removal process. To the relative low initial concentration 50.0μgL -1 , MnFe 2 O 4 material sorbent can still decrease As or Sb below US EPA's drinking water standard limit. The separation of MnFe 2 O 4 was mainly relied on the flow rate and the amount of steel wools in the HGMS system. At a flow rate 1Lmin -1 and 5% steel wools filling rate, the removal efficacies of As and Sb in natural water with the system were achieved to be 94.6% and 76.8%, respectively. At the meantime, nearly 100% micro-sized MnFe 2 O 4 solid in the continuous field was readily to be separated via HGMS system. In a combination with the experiment results and finite element simulation, the separation was seemed to be independent on the magnetic field intensity, and the maximum separation capacities in various conditions were well predicted using the Thomas model (R 2 =0.87-0.99). Copyright © 2017 Elsevier B.V. All rights reserved.

  16. High-gradient experiment on X-band disk-loaded structures

    International Nuclear Information System (INIS)

    Higo, T.; Taniuchi, T.; Yamamoto, M.; Odagiri, J.; Tokumoto, S.; Mizuno, H.; Takata, K.; Wilson, I.; Wuensch, W.

    1993-09-01

    The high-gradient performance of two travelling-wave X-band accelerating structures 20 cm long has been studied. One of the structures, KEK, was conditioned up to an average accelerating gradient (Eav) of 68 MV/m in 600 hours, while the other, CERN, reached 85 MV/m in 50 hours. In the latter case the maximum output power was fed from the SLED system and the maximum field inside the structure was 138 MV/m. This maximum level was limited by the available power from the klystron. Operation at the Eav=50 MV/m level was found to be stable for both structures. The associated dark current at this level was less than a few μA for CERN but 20 to 30 μA for KEK. Since the two electrical designs are almost the same the difference in dark current must be attributed to the difference in the two fabrication techniques. Modified Fowler-Northeim plots of downstream dark current showed a change of slope, a kink, around 50 to 60 MV/m above which the field enhancement factor was substantially increased. (author)

  17. High-gradient magnetic separation for the treatment of high-level radioactive wastes

    International Nuclear Information System (INIS)

    Ebner, A.D.; Ritter, J.A.; Nunez, L.

    1999-01-01

    Argonne National Laboratory is developing an open-gradient magnetic separation (OGMS) system to fractionate and remove nonglass-forming species from high-level radioactive wastes (HLW); however, to avoid clogging, OGMS may require high-gradient magnetic separation (HGMS) as a pretreatment to remove the most magnetic species from the HLW. In this study, the feasibility of using HGMS in the pretreatment of HLW was demonstrated. A HLW simulant of hanford's C-103 tank waste, which contained precipitate hydroxides and oxides of Fe, Al, Si, and Ca, was used. Preliminary fractionation results from a 0.3-T bench-scale HGMS unit showed that a significant amount of Fe could be removed from the HLW simulant. Between 1 and 2% of the total Fe in the sludge was removed during each stage, with over 18.5% removed in the 13 stages that were carried out. Also, in each stage, the magnetically retained fraction contained about 20% more Fe than the untreated HLW; however, it also contained a significant amount of SiO 2 in relatively large particles. This indicated that SiO 2 was acting possibly as a nucleation agent for Fe (i.e., an Fe adsorbent) and that the fractionation was based more on size than on magnetic susceptibility

  18. High gradient magnetic separation of upconverting lanthanide nanophosphors based on their intrinsic paramagnetism

    Energy Technology Data Exchange (ETDEWEB)

    Arppe, Riikka, E-mail: riikka.arppe@utu.fi; Salovaara, Oskari; Mattsson, Leena; Lahtinen, Satu; Valta, Timo; Riuttamaeki, Terhi; Soukka, Tero [University of Turku, Department of Biotechnology (Finland)

    2013-09-15

    Photon upconverting nanophosphors (UCNPs) have the unique luminescent property of converting low-energy infrared light into visible emission which can be widely utilized in nanoreporter and imaging applications. For the use as reporters in these applications, the UCNPs must undergo a series of surface modification and bioconjugation reactions. Efficient purification methods are required to remove the excess reagents and biomolecules from the nanophosphor solution after each step to yield highly responsive reporters for sensitive bioanalytical assays. However, as the particle size of the UCNPs approaches the size of biomolecules, the handling of these reporters becomes cumbersome with traditional purification methods such as centrifugation. Here we introduce a novel approach for purification of bioconjugated 32-nm NaYF{sub 4}: Yb{sup 3+}, Er{sup 3+}-nanophosphors from excess unbound biomolecules utilizing high gradient magnetic separation (HGMS)-system constructed from permanent super magnets which produce magnetic gradients in a magnetizable steel wool matrix amplifying the magnetic field. The non-magnetic biomolecules flowed straight through the magnetized HGMS-column while the UCNPs were eluted only after the magnetic field was removed. In the UCNPs the luminescent centers, i.e., lanthanide-ion dopants are responsible for the strong upconversion luminescence, but in addition they are also paramagnetic. In this study we have shown that the presence of these weakly paramagnetic luminescent lanthanides actually also enables the use of HGMS to capture the UCNPs without incorporating additional optically inactive magnetic core into them.

  19. New technology based on clamping for high gradient radio frequency photogun

    Science.gov (United States)

    Alesini, David; Battisti, Antonio; Ferrario, Massimo; Foggetta, Luca; Lollo, Valerio; Ficcadenti, Luca; Pettinacci, Valerio; Custodio, Sean; Pirez, Eylene; Musumeci, Pietro; Palumbo, Luigi

    2015-09-01

    High gradient rf photoguns have been a key development to enable several applications of high quality electron beams. They allow the generation of beams with very high peak current and low transverse emittance, satisfying the tight demands for free-electron lasers, energy recovery linacs, Compton/Thomson sources and high-energy linear colliders. In the present paper we present the design of a new rf photogun recently developed in the framework of the SPARC_LAB photoinjector activities at the laboratories of the National Institute of Nuclear Physics in Frascati (LNF-INFN, Italy). This design implements several new features from the electromagnetic point of view and, more important, a novel technology for its realization that does not involve any brazing process. From the electromagnetic point of view the gun presents high mode separation, low peak surface electric field at the iris and minimized pulsed heating on the coupler. For the realization, we have implemented a novel fabrication design that, avoiding brazing, strongly reduces the cost, the realization time and the risk of failure. Details on the electromagnetic design, low power rf measurements and high power radiofrequency and beam tests performed at the University of California in Los Angeles (UCLA) are discussed in the paper.

  20. The UCLA/SLAC Ultra-High Gradient Cerenkov Wakefield Accelerator Experiment

    CERN Document Server

    Thompson, Matthew C; Hogan, Mark; Ischebeck, Rasmus; Muggli, Patric; Rosenzweig, James E; Scott, A; Siemann, Robert; Travish, Gil; Walz, Dieter; Yoder, Rodney

    2005-01-01

    An experiment is planned to study the performance of dielectric Cerenkov wakefield accelerating structures at extremely high gradients in the GV/m range. This new UCLA/SLAC collaboration will take advantage of the unique SLAC FFTB electron beam and its demonstrated ultra-short pulse lengths and high currents (e.g., sz = 20 μm at Q = 3 nC). The electron beam will be focused down and sent through varying lengths of fused silica capillary tubing with two different sizes: ID = 200 μm / OD = 325 μm and ID = 100 μm / OD = 325 μm. The pulse length of the electron beam will be varied in order to alter the accelerating gradient and probe the breakdown threshold of the dielectric structures. In addition to breakdown studies, we plan to collect and measure coherent Cerenkov radiation emitted from the capillary tube to gain information about the strength of the accelerating fields. Status and progress on the experiment are reported.

  1. High gradient magnetic separation of upconverting lanthanide nanophosphors based on their intrinsic paramagnetism

    International Nuclear Information System (INIS)

    Arppe, Riikka; Salovaara, Oskari; Mattsson, Leena; Lahtinen, Satu; Valta, Timo; Riuttamäki, Terhi; Soukka, Tero

    2013-01-01

    Photon upconverting nanophosphors (UCNPs) have the unique luminescent property of converting low-energy infrared light into visible emission which can be widely utilized in nanoreporter and imaging applications. For the use as reporters in these applications, the UCNPs must undergo a series of surface modification and bioconjugation reactions. Efficient purification methods are required to remove the excess reagents and biomolecules from the nanophosphor solution after each step to yield highly responsive reporters for sensitive bioanalytical assays. However, as the particle size of the UCNPs approaches the size of biomolecules, the handling of these reporters becomes cumbersome with traditional purification methods such as centrifugation. Here we introduce a novel approach for purification of bioconjugated 32-nm NaYF 4 : Yb 3+ , Er 3+ -nanophosphors from excess unbound biomolecules utilizing high gradient magnetic separation (HGMS)-system constructed from permanent super magnets which produce magnetic gradients in a magnetizable steel wool matrix amplifying the magnetic field. The non-magnetic biomolecules flowed straight through the magnetized HGMS-column while the UCNPs were eluted only after the magnetic field was removed. In the UCNPs the luminescent centers, i.e., lanthanide-ion dopants are responsible for the strong upconversion luminescence, but in addition they are also paramagnetic. In this study we have shown that the presence of these weakly paramagnetic luminescent lanthanides actually also enables the use of HGMS to capture the UCNPs without incorporating additional optically inactive magnetic core into them

  2. Effects of high-gradient magnetic fields on living cell machinery

    International Nuclear Information System (INIS)

    Zablotskii, V; Lunov, O; Kubinova, S; Polyakova, T; Dejneka, A; Sykova, E

    2016-01-01

    A general interest in biomagnetic effects is related to fundamental studies of the influence of magnetic fields on living objects on the cellular and whole organism levels. Emerging technologies offer new directions for the use of high-gradient magnetic fields to control cell machinery and to understand the intracellular biological processes of the emerging field of nanomedicine. In this review we aim at highlighting recent advances made in identifying fundamental mechanisms by which magnetic gradient forces act on cell fate specification and cell differentiation. The review also provides an analysis of the currently available magnetic systems capable of generating magnetic fields with spatial gradients of up to 10 MT m −1 , with the focus on their suitability for use in cell therapy. Relationships between experimental factors and underlying biophysical mechanisms and assumptions that would ultimately lead to a deeper understanding of cell machinery and the development of more predictive models for the evaluation of the effects of magnetic fields on cells, tissue and organisms are comprehensively discussed. (topical review)

  3. Particle capture efficiency in a multi-wire model for high gradient magnetic separation

    KAUST Repository

    Eisenträger, Almut

    2014-07-21

    High gradient magnetic separation (HGMS) is an efficient way to remove magnetic and paramagnetic particles, such as heavy metals, from waste water. As the suspension flows through a magnetized filter mesh, high magnetic gradients around the wires attract and capture the particles removing them from the fluid. We model such a system by considering the motion of a paramagnetic tracer particle through a periodic array of magnetized cylinders. We show that there is a critical Mason number (ratio of viscous to magnetic forces) below which the particle is captured irrespective of its initial position in the array. Above this threshold, particle capture is only partially successful and depends on the particle\\'s entry position. We determine the relationship between the critical Mason number and the system geometry using numerical and asymptotic calculations. If a capture efficiency below 100% is sufficient, our results demonstrate how operating the HGMS system above the critical Mason number but with multiple separation cycles may increase efficiency. © 2014 AIP Publishing LLC.

  4. Theory of factors limiting high gradient operation of warm accelerating structures

    Energy Technology Data Exchange (ETDEWEB)

    Nusinovich, Gregory S. [University of Maryland; Antonsen, Thomas M. [University of Maryland; Kishek, Rami [University of Maryland

    2014-07-25

    This final report summarizes the research performed during the time period from 8/1/2010 to 7/31/2013. It consists of two parts describing our studies in two directions: (a) analysis of factors limiting operation of dielectric-loaded accelerating (DLA) structures where the main problem is the occurrence of multipactor on dielectric surfaces, and (b) studies of effects associated with either RF magnetic or RF electric fields which may cause the RF breakdown in high-gradient metallic accelerating structures. In the studies of DLA structures, at least, two accomplishments should be mentioned: the development of a 3D non-stationary, self-consistent code describing the multipactor phenomena and yielding very good agreement with some experimental data obtained in joint ANL/NRL experiments. In the metallic structures, such phenomena as the heating and melting of micro-particles (metallic dust) by RF electric and magnetic fields in single-shot and rep-rate regimes is analyzed. Also, such processes in micro-protrusions on the structure surfaces as heating and melting due to the field emitted current and the Nottingham effect are thoroughly investigated with the account for space charge of emitted current on the field emission from the tip.

  5. Roughness analysis applied to niobium thin films grown on MgO(001) surfaces for superconducting radio frequency cavity applications

    OpenAIRE

    D. B. Beringer; W. M. Roach; C. Clavero; C. E. Reece; R. A. Lukaszew

    2013-01-01

    This paper describes surface studies to address roughness issues inherent to thin film coatings deposited onto superconducting radio frequency (SRF) cavities. This is particularly relevant for multilayered thin film coatings that are being considered as a possible scheme to overcome technical issues and to surpass the fundamental limit of ∼50  MV/m accelerating gradient achievable with bulk niobium. In 2006, a model by Gurevich [Appl. Phys. Lett. 88, 012511 (2006)APPLAB0003-695110.1063/1.2162...

  6. Macroinvertebrate community responses to gravel augmentation in a high-gradient, Southeastern regulated river

    Energy Technology Data Exchange (ETDEWEB)

    McManamay, Ryan A [ORNL; Orth, Dr. Donald J [Virginia Polytechnic Institute and State University; Dolloff, Dr. Charles A [United States Department of Agriculture (USDA), United States Forest Service (USFS) and Virginia Pol

    2013-01-01

    Sediment transport, one of the key processes of river systems, is altered or stopped by dams, leaving lower river reaches barren of sand and gravel, both of which are essential habitat for fish and macroinvertebrates. One way to compensate for losses in sediment is to supplement gravel to river reaches below impoundments. Because gravel addition has become a widespread practice, it is essential to evaluate the biotic response to restoration projects in order to improve the efficacy of future applications. The purpose of our study was to evaluate the response of the macroinvertebrate community to gravel addition in a high-gradient, regulated river in western North Carolina. We collected benthic macroinvertebrate samples from gravel-enhanced areas and unenhanced areas for 1 season before gravel addition, and for 4 seasons afterwards. Repeated measures multivariate analysis of variance indicated that the responses of macroinvertebrates to gravel addition were generally specific to individual taxa or particular functional feeding groups and did not lead to consistent patterns in overall family richness, diversity, density, or evenness. Non-metric multi-dimensional scaling showed that shifts in macroinvertebrate community composition were temporary and dependent upon site conditions and season. Correlations between macroinvertebrate response variables and substrate microhabitat variables existed with or without the inclusion of data from enhanced areas, which suggests that substrate-biotic relationships were present before gravel addition. A review of the current literature suggests that the responses of benthic macroinvertebrates to substrate restoration are inconsistent and dependent upon site conditions and the degree habitat improvement of pre-restoration site conditions.

  7. Feasibility of turbidity removal by high-gradient superconducting magnetic separation.

    Science.gov (United States)

    Zeng, Hua; Li, Yiran; Xu, Fengyu; Jiang, Hao; Zhang, Weimin

    2015-01-01

    Several studies have focused on pollutant removal by magnetic seeding and high-gradient superconducting magnetic separation (HGSMS). However, few works reported the application of HGSMS for treating non-magnetic pollutants by an industrial large-scale system. The feasibility of turbidity removal by a 600 mm bore superconducting magnetic separation system was evaluated in this study. The processing parameters were evaluated by using a 102 mm bore superconducting magnetic separation system that was equipped with the same magnetic separation chamber that was used in the 600 mm bore system. The double-canister system was used to process water pollutants. Analytical grade magnetite was used as a magnetic seed and the turbidity of the simulated raw water was approximately 110 NTU, and the effects of polyaluminum chloride (PAC) and magnetic seeds on turbidity removal were evaluated. The use of more PAC and magnetic seeds had few advantages for the HGSMS at doses greater than 8 and 50 mg/l, respectively. A magnetic intensity of 5.0 T was beneficial for HGSMS, and increasing the flow rate through the steel wool matrix decreased the turbidity removal efficiency. In the breakthrough experiments, 90% of the turbidity was removed when 100 column volumes were not reached. The processing capacity of the 600 mm bore industry-scale superconducting magnetic separator for turbidity treatment was approximately 78.0 m(3)/h or 65.5 × 10(4) m(3)/a. The processing cost per ton of water for the 600 mm bore system was 0.1 $/t. Thus, the HGSMS separator could be used in the following special circumstances: (1) when adequate space is not available for traditional water treatment equipment, especially the sedimentation tank, and (2) when decentralized sewage treatment HGSMS systems are easier to transport and install.

  8. Proof-of-principle demonstration of Nb3Sn superconducting radiofrequency cavities for high Q0 applications

    Science.gov (United States)

    Posen, S.; Liepe, M.; Hall, D. L.

    2015-02-01

    Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. This contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb3Sn. In this paper, we present results for single cell cavities coated with Nb3Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q0 out to medium fields was reproducible, resulting in an average quench field of 14 MV/m and an average 4.2 K Q0 at quench of 8 × 109. In each case, the peak surface magnetic field at quench was well above Hc1, showing that it is not a limiting field in these cavities. The coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that—taking into account the thermodynamic efficiency of the cryogenic plant—the 4.2 K Q0 values obtained meet the AC power consumption requirements of state-of-the-art high duty factor accelerators, making this a proof-of-principle demonstration for Nb3Sn cavities in future applications.

  9. On a possibility of using a superconducting cavity in the RF system of the storage ring LESR-N100

    CERN Document Server

    Androsov, V P; Telegin, Yu P

    2002-01-01

    In the Kharkov Institute of Physics and Technology the design project of the 200 MeV electron storage ring LESR-N100 is under development. The essential feature of this facility is the large beam energy spread (of about 1%). To ensure a reasonable beam lifetime the RF-system should provide the accelerating voltage of about 0.5 MV, while the total energy losses do not exceed approx 700 eV/turn. The power dissipated in two 700 MHz normal-conducting (NC) cavities much exceeds the power transmitted to the beam. We considered a possibility to use in LESR-N100 a high-Q superconducting RF-cavity (SRF-cavity) in which the dissipated power is the same order of magnitude as the beam-transmitted power. The studies show that the system with SRF-cavity cannot operate in the standard mode when the cavity is matched to the power transmission line at some nominal beam current. The optimal operation mode with high overcoupling is proposed that requires the RF-power one order of magnitude less than in the case of Nc-cavities.

  10. Sample preparation and biomass determination of SRF model mixture using cryogenic milling and the adapted balance method

    Energy Technology Data Exchange (ETDEWEB)

    Schnöller, Johannes, E-mail: johannes.schnoeller@chello.at; Aschenbrenner, Philipp; Hahn, Manuel; Fellner, Johann; Rechberger, Helmut

    2014-11-15

    Highlights: • An alternative sample comminution procedure for SRF is tested. • Proof of principle is shown on a SRF model mixture. • The biogenic content of the SRF is analyzed with the adapted balance method. • The novel method combines combustion analysis and a data reconciliation algorithm. • Factors for the variance of the analysis results are statistically quantified. - Abstract: The biogenic fraction of a simple solid recovered fuel (SRF) mixture (80 wt% printer paper/20 wt% high density polyethylene) is analyzed with the in-house developed adapted balance method (aBM). This fairly new approach is a combination of combustion elemental analysis (CHNS) and a data reconciliation algorithm based on successive linearisation for evaluation of the analysis results. This method shows a great potential as an alternative way to determine the biomass content in SRF. However, the employed analytical technique (CHNS elemental analysis) restricts the probed sample mass to low amounts in the range of a few hundred milligrams. This requires sample comminution to small grain sizes (<200 μm) to generate representative SRF specimen. This is not easily accomplished for certain material mixtures (e.g. SRF with rubber content) by conventional means of sample size reduction. This paper presents a proof of principle investigation of the sample preparation and analysis of an SRF model mixture with the use of cryogenic impact milling (final sample comminution) and the adapted balance method (determination of biomass content). The so derived sample preparation methodology (cutting mills and cryogenic impact milling) shows a better performance in accuracy and precision for the determination of the biomass content than one solely based on cutting mills. The results for the determination of the biogenic fraction are within 1–5% of the data obtained by the reference methods, selective dissolution method (SDM) and {sup 14}C-method ({sup 14}C-M)

  11. Ultrastructure of pea and cress root statocytes exposed to high gradient magnetic field

    Science.gov (United States)

    Belyavskaya, N. A.; Chernishov, V. I.; Polishchuk, O. V.; Kondrachuk, A. V.

    As it was demonstrated by Kuznetsov & Hasenstein (1996) the high gradient magnetic field (HGMF) can produce a ponderomotive force that results in displacements of amyloplasts and causes the root response similar to the graviresponse. It was suggested that the HGMF could allow to imitate the effects of gravity in microgravity and/or change them in laboratory conditions correspondingly, as well as to study statolith-related processes in graviperception. Therefore, the correlation between the direction of the ponderomotive force resulting in statolith displacements and the direction of the HGMF-induced plant curvature can be the serious argument to support this suggestion and needs the detailed ultrastructural analysis. Seeds of dicotyledon Pisum sativum L. cv. Damir-2 and monocotyledon Lepidium sativum L. cv. P896 were soaked and grown in a vertical position on moist filter paper in chambers at room temperature. Tips of primary roots of vertical control, gravistimulated and exposed to HGMF seedlings were fixed for electron microscopy using conventional techniques. At ultrastructural level, we observed no significant changes in the volume of the individual statocytes or amyloplasts, relative volumes of cellular organelles (except vacuoles), number of amyloplasts per statocyte or surface area of endoplasmic reticulum. No consistent contacts between amyloplasts and any cellular structures, including plasma membrane, were revealed at any stage of magneto- and gravistimulation. By 5 min after onset of magnetostimulation, amyloplasts were located along cell wall distant from magnets. In HGMF, the locations of amyloplasts in columella cells were similar to those in horizontally-oriented roots up to 1 h stimulation. In the latter case, there were sometimes cytoplasmic spherical bodies with a dense vesicle-rich cytoplasm in pea statocytes, which were absent in seedlings exposed to HGMF. In cress root statocytes, both gravi- and magnetostimulation were found to cause the

  12. Evidence for tension-based regulation of Drosophila MAL and SRF during invasive cell migration.

    Science.gov (United States)

    Somogyi, Kálmán; Rørth, Pernille

    2004-07-01

    Cells migrating through a tissue exert force via their cytoskeleton and are themselves subject to tension, but the effects of physical forces on cell behavior in vivo are poorly understood. Border cell migration during Drosophila oogenesis is a useful model for invasive cell movement. We report that this migration requires the activity of the transcriptional factor serum response factor (SRF) and its cofactor MAL-D and present evidence that nuclear accumulation of MAL-D is induced by cell stretching. Border cells that cannot migrate lack nuclear MAL-D but can accumulate it if they are pulled by other migrating cells. Like mammalian MAL, MAL-D also responds to activated Diaphanous, which affects actin dynamics. MAL-D/SRF activity is required to build a robust actin cytoskeleton in the migrating cells; mutant cells break apart when initiating migration. Thus, tension-induced MAL-D activity may provide a feedback mechanism for enhancing cytoskeletal strength during invasive migration.

  13. Results from the first single cell Nb3Sn cavity coatings at JLab

    Energy Technology Data Exchange (ETDEWEB)

    Eremeev, Grigory [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2015-09-01

    Nb3Sn is a promising superconducting material for SRF applications and has the potential to exceed the limitations of niobium. We have used the recently commissioned Nb3Sn coating system to investigate Nb3Sn coatings on several single cell cavities by applying the same coating procedure on several different single cells with different history and pre-coating surface preparation. We report on our findings with four 1.5 GHz CEBAF-shape single cell and one 1.3 GHz ILC-shape single cavities that were coated, inspected, and tested.

  14. Probing the fundamental limit of niobium in high radiofrequency fields by dual mode excitation in superconducting radiofrequency cavities

    International Nuclear Information System (INIS)

    Eremeev, Grigory; Geng, Rongli; Palczewski, Ari

    2011-01-01

    We have studied thermal breakdown in several multicell superconducting radiofrequency cavity by simultaneous excitation of two TM 010 passband modes. Unlike measurements done in the past, which indicated a clear thermal nature of the breakdown, our measurements present a more complex picture with interplay of both thermal and magnetic effects. JLab LG-1 that we studied was limited at 40.5 MV/m, corresponding to B peak = 173 mT, in 89 mode. Dual mode measurements on this quench indicate that this quench is not purely magnetic, and so we conclude that this field is not the fundamental limit in SRF cavities

  15. Physics and chemistry of niobium materials in the context of superconducting RF cavity applications

    International Nuclear Information System (INIS)

    Roy, S.B.

    2016-01-01

    Superconducting radio frequency (SCRF) cavities excel over the normal conducting RF cavities in the long pulse or continuous wave high energy particle accelerations, and niobium (Nb) is currently the material of choice for fabrication of such SCRF cavities. However the accelerating gradients attained in the Nb SCRF cavities deployed in various high energy particle accelerators are significantly below the theoretical limit predicted by the superconducting properties of Nb. Thus it is very important to understand the physics and chemistry of Nb materials in some details so as to maximize the SCRF cavity performance. This abstract will discuss some issues which help in the development of high gradient and energy efficient Nb SCRF cavities in a cost effective manner. (author)

  16. Gas Generation Testing of Spherical Resorcinol-Formaldehyde (sRF) Resin

    Energy Technology Data Exchange (ETDEWEB)

    Colburn, Heather A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bryan, Samuel A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Camaioni, Donald M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Mahoney, Lenna A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Adami, Susan R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2018-01-19

    This report describes gas generation testing of the spherical resorcinol-formaldehyde (sRF) resin that was conducted to support the technology maturation of the LAWPS facility. The current safety basis for the LAWPS facility is based primarily on two studies that had limited or inconclusive data sets. The two studies indicated a 40% increase in hydrogen generation rate of water (as predicted by the Hu model) with sRF resin over water alone. However, the previous studies did not test the range of conditions (process fluids and temperatures) that are expected in the LAWPS facility. Additionally, the previous studies did not obtain replicate test results or comparable liquid-only control samples. All of the testing described in this report, conducted with water, 0.45M nitric acid, and waste simulants with and without sRF resin, returned hydrogen generation rates that are within the current safety basis for the facility of 1.4 times the Hu model output for water.

  17. Segmented trapped vortex cavity

    Science.gov (United States)

    Grammel, Jr., Leonard Paul (Inventor); Pennekamp, David Lance (Inventor); Winslow, Jr., Ralph Henry (Inventor)

    2010-01-01

    An annular trapped vortex cavity assembly segment comprising includes a cavity forward wall, a cavity aft wall, and a cavity radially outer wall there between defining a cavity segment therein. A cavity opening extends between the forward and aft walls at a radially inner end of the assembly segment. Radially spaced apart pluralities of air injection first and second holes extend through the forward and aft walls respectively. The segment may include first and second expansion joint features at distal first and second ends respectively of the segment. The segment may include a forward subcomponent including the cavity forward wall attached to an aft subcomponent including the cavity aft wall. The forward and aft subcomponents include forward and aft portions of the cavity radially outer wall respectively. A ring of the segments may be circumferentially disposed about an axis to form an annular segmented vortex cavity assembly.

  18. Modulation of monocytic leukemia cell function and survival by high gradient magnetic fields and mathematical modeling studies.

    Science.gov (United States)

    Zablotskii, Vitalii; Syrovets, Tatiana; Schmidt, Zoe W; Dejneka, Alexandr; Simmet, Thomas

    2014-03-01

    The influence of spatially modulated high gradient magnetic fields on cellular functions of human THP-1 leukemia cells is studied. We demonstrate that arrays of high-gradient micrometer-sized magnets induce i) cell swelling, ii) prolonged increased ROS production, and iii) inhibit cell proliferation, and iv) elicit apoptosis of THP-1 monocytic leukemia cells in the absence of chemical or biological agents. Mathematical modeling indicates that mechanical stress exerted on the cells by high magnetic gradient forces is responsible for triggering cell swelling and formation of reactive oxygen species followed by apoptosis. We discuss physical aspects of controlling cell functions by focused magnetic gradient forces, i.e. by a noninvasive and nondestructive physical approach. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Cryogenic infrastructure for Fermilab's ILC vertical cavity test facility

    International Nuclear Information System (INIS)

    Carcagno, R.; Ginsburg, C.; Huang, Y.; Norris, B.; Ozelis, J.; Peterson, T.; Poloubotko, V.; Rabehl, R.; Sylvester, C.; Wong, M.; Fermilab

    2006-01-01

    Fermilab is building a Vertical Cavity Test Facility (VCTF) to provide for R and D and pre-production testing of bare 9-cell, 1.3-GHz superconducting RF (SRF) cavities for the International Linear Collider (ILC) program. This facility is located in the existing Industrial Building 1 (IB1) where the Magnet Test Facility (MTF) also resides. Helium and nitrogen cryogenics are shared between the VCTF and MTF including the existing 1500-W at 4.5-K helium refrigerator with vacuum pumping for super-fluid operation (125-W capacity at 2-K). The VCTF is being constructed in multiple phases. The first phase is scheduled for completion in mid 2007, and includes modifications to the IB1 cryogenic infrastructure to allow helium cooling to be directed to either the VCTF or MTF as scheduling demands require. At this stage, the VCTF consists of one Vertical Test Stand (VTS) cryostat for the testing of one cavity in a 2-K helium bath. Planning is underway to provide a total of three Vertical Test Stands at VCTF, each capable of accommodating two cavities. Cryogenic infrastructure improvements necessary to support these additional VCTF test stands include a dedicated ambient temperature vacuum pump, a new helium purification skid, and the addition of helium gas storage. This paper describes the system design and initial cryogenic operation results for the first VCTF phase, and outlines future cryogenic infrastructure upgrade plans for expanding to three Vertical Test Stands

  20. CRYOGENIC INFRASTRUCTURE FOR FERMILAB'S ILC VERTICAL CAVITY TEST FACILITY

    International Nuclear Information System (INIS)

    Carcagno, R.; Ginsburg, C.; Huang, Y.; Norris, B.; Ozelis, J.; Peterson, T.; Poloubotko, V.; Rabehl, R.; Sylvester, C.; Wong, M.

    2008-01-01

    Fermilab is building a Vertical Cavity Test Facility (VCTF) to provide for R and D and pre-production testing of bare 9-cell, 1.3-GHz superconducting RF (SRF) cavities for the International Linear Collider (ILC) program. This facility is located in the existing Industrial Building 1 (IB1) where the Magnet Test Facility (MTF) also resides. Helium and nitrogen cryogenics are shared between the VCTF and MTF including the existing 1500-W at 4.5-K helium refrigerator with vacuum pumping for super-fluid operation (125-W capacity at 2-K). The VCTF is being constructed in multiple phases. The first phase is scheduled for completion in mid 2007, and includes modifications to the IB1 cryogenic infrastructure to allow helium cooling to be directed to either the VCTF or MTF as scheduling demands require. At this stage, the VCTF consists of one Vertical Test Stand (VTS) cryostat for the testing of one cavity in a 2-K helium bath. Planning is underway to provide a total of three Vertical Test Stands at VCTF, each capable of accommodating two cavities. Cryogenic infrastructure improvements necessary to support these additional VCTF test stands include a dedicated ambient temperature vacuum pump, a new helium purification skid, and the addition of helium gas storage. This paper describes the system design and initial cryogenic operation results for the first VCTF phase, and outlines future cryogenic infrastructure upgrade plans for expanding to three Vertical Test Stands

  1. Plasma processing of large curved surfaces for superconducting rf cavity modification

    Directory of Open Access Journals (Sweden)

    J. Upadhyay

    2014-12-01

    Full Text Available Plasma-based surface modification of niobium is a promising alternative to wet etching of superconducting radio frequency (SRF cavities. We have demonstrated surface layer removal in an asymmetric nonplanar geometry, using a simple cylindrical cavity. The etching rate is highly correlated with the shape of the inner electrode, radio-frequency (rf circuit elements, gas pressure, rf power, chlorine concentration in the Cl_{2}/Ar gas mixtures, residence time of reactive species, and temperature of the cavity. Using variable radius cylindrical electrodes, large-surface ring-shaped samples, and dc bias in the external circuit, we have measured substantial average etching rates and outlined the possibility of optimizing plasma properties with respect to maximum surface processing effect.

  2. Simulation of the High-Pass Filter for 56MHz Cavity for RHIC

    International Nuclear Information System (INIS)

    Wu, Q.; Ben-Zvi, I.

    2010-01-01

    The 56MHz Superconducting RF (SRF) cavity for RHIC places high demands High Order Mode (HOM) damping, as well as requiring a high field at gap with fundamental mode frequency. The damper of 56MHz cavity is designed to extract all modes to the resistance load outside, including the fundamental mode. Therefore, the circuit must incorporate a high-pass filter to reflect back the fundamental mode into the cavity. In this paper, we show the good frequency response map obtained from our filter's design. We extract a circuit diagram from the microwave elements that simulate well the frequency spectrum of the finalized filter. We also demonstrate that the power dissipation on the filter over its frequency range is small enough for cryogenic cooling.

  3. Physical Properties of Niobium and Specifications for Fabrication of Superconducting Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Antoine, C.; Foley, M.; Dhanaraj, N.; /Fermilab

    2011-07-01

    It is important to distinguish among the properties of niobium, the ones that are related to the cavity's SRF performances, the formability of the material, and the mechanical behavior of the formed cavity. In general, the properties that dictate each of the above mentioned characteristics have a detrimental effect on one another and in order to preserve the superconducting properties without subduing the mechanical behavior, a balance has to be established. Depending on the applications, some parameters become less important and an understanding of the physical origin of the requirements might help in this optimization. SRF applications require high purity niobium (high RRR), but pure niobium is very soft from fabrication viewpoint. Moreover conventional fabrication techniques tend to override the effects of any metallurgical process meant to strengthen it. As those treatments dramatically affect the forming of the material they should be avoided. These unfavorable mechanical properties have to be accounted for in the design of the cavities rather than in the material specification. The aim of this paper is to review the significance of the important mechanical properties used to characterize niobium and to present the optimal range of values. Most of the following information deals with the specification of sheets for cell forming unless otherwise noted.

  4. Physical Properties of Niobium and Specifications for Fabrication of Superconducting Cavities

    International Nuclear Information System (INIS)

    Antoine, C.; Foley, M.; Dhanaraj, N.

    2011-01-01

    It is important to distinguish among the properties of niobium, the ones that are related to the cavity's SRF performances, the formability of the material, and the mechanical behavior of the formed cavity. In general, the properties that dictate each of the above mentioned characteristics have a detrimental effect on one another and in order to preserve the superconducting properties without subduing the mechanical behavior, a balance has to be established. Depending on the applications, some parameters become less important and an understanding of the physical origin of the requirements might help in this optimization. SRF applications require high purity niobium (high RRR), but pure niobium is very soft from fabrication viewpoint. Moreover conventional fabrication techniques tend to override the effects of any metallurgical process meant to strengthen it. As those treatments dramatically affect the forming of the material they should be avoided. These unfavorable mechanical properties have to be accounted for in the design of the cavities rather than in the material specification. The aim of this paper is to review the significance of the important mechanical properties used to characterize niobium and to present the optimal range of values. Most of the following information deals with the specification of sheets for cell forming unless otherwise noted.

  5. Laser Processing on the Surface of Niobium Superconducting Radio-Frequency Accelerator Cavities

    Science.gov (United States)

    Singaravelu, Senthilraja; Klopf, Michael; Krafft, Geoffrey; Kelley, Michael

    2011-03-01

    Superconducting Radio frequency (SRF) niobium cavities are at the heart of an increasing number of particle accelerators.~ Their performance is dominated by a several nm thick layer at the interior surface. ~Maximizing its smoothness is found to be critical and aggressive chemical treatments are employed to this end.~ We describe laser-induced surface melting as an alternative ``greener'' approach.~ Modeling guided selection of parameters for irradiation with a Q-switched Nd:YAG laser.~ The resulting topography was examined by SEM, AFM and Stylus Profilometry.

  6. Insights to Superconducting Radio-Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques

    Science.gov (United States)

    Ford, Denise Christine

    Insights to the fundamental processes that occur during the manufacturing of niobium superconducting radio-frequency (SRF) cavities are provided via analyses of density functional theory calculations and Raman, infrared, and nuclear magnetic resonance (NMR) spectra. I show that during electropolishing fluorine is bound and released by the reaction of the acid components in the solution: HF + H2SO4 HFSO3 + H2O. This result implies that new recipes can possibly be developed on the principle of controlled release of fluorine by a chemical reaction. I also show that NMR or Raman spectroscopy can be used to monitor the free fluorine when polishing with the standard electropolishing recipe. Density functional theory was applied to calculate the properties of common processing impurities---hydrogen, oxygen, nitrogen, and carbon---in the niobium. These impurities lower the superconducting transition temperature of niobium, and hydride precipitates are at best weakly superconducting. I modeled several of the niobium hydride phases relevant to SRF cavities, and explain the phase changes in the niobium hydrogen system based on the charge transfer between niobium and hydrogen and the strain field inside of the niobium. I also present evidence for a niobium lattice vacancy serving as a nucleation center for hydride phase formation. In considering the other chemical impurities in niobium, I show that the absorption of oxygen into a niobium lattice vacancy is preferred over the absorption of hydrogen, which indicates that oxygen can block these phase nucleation centers. I also show that dissolved oxygen atoms can trap dissolved hydrogen atoms to prevent niobium hydride phase formation. Nitrogen and carbon were studied in less depth, but behaved similarly to oxygen. Based on these results and a literature survey, I propose a mechanism for the success of the low-temperature anneal applied to niobium SRF cavities. Finally, I present the beginning of a model to describe magnetic

  7. Insights to Superconducting Radio-Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ford, Denise Christine [Northwestern Univ., Evanston, IL (United States)

    2013-03-01

    Insights to the fundamental processes that occur during the manufacturing of niobium superconducting radio-frequency (SRF) cavities are provided via analyses of density functional theory calculations and Raman, infrared, and nuclear magnetic resonance (NMR) spectra. I show that during electropolishing fluorine is bound and released by the reaction of the acid components in the solution: HF + H2SO4 <-> HFSO3 + H2O. This result implies that new recipes can possibly be developed on the principle of controlled release of fluorine by a chemical reaction. I also show that NMR or Raman spectroscopy can be used to monitor the free fluorine when polishing with the standard electropolishing recipe. Density functional theory was applied to calculate the properties of common processing impurities – hydrogen, oxygen, nitrogen, and carbon – in the niobium. These impurities lower the superconducting transition temperature of niobium, and hydride precipitates are at best weakly superconducting. I modeled several of the niobium hydride phases relevant to SRF cavities, and explain the phase changes in the niobium hydrogen system based on the charge transfer between niobium and hydrogen and the strain field inside of the niobium. I also present evidence for a niobium lattice vacancy serving as a nucleation center for hydride phase formation. In considering the other chemical impurities in niobium, I show that the absorption of oxygen into a niobium lattice vacancy is preferred over the absorption of hydrogen, which indicates that oxygen can block these phase nucleation centers. I also show that dissolved oxygen atoms can trap dissolved hydrogen atoms to prevent niobium hydride phase formation. Nitrogen and carbon were studied in less depth, but behaved similarly to oxygen. Based on these results and a literature survey, I propose a mechanism for the success of the low-temperature anneal applied to niobium SRF cavities. Finally, I

  8. RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rolland

    2014-09-21

    Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

  9. The external Q factor of a dual-feed coupling for superconducting radio frequency cavities: Theoretical and experimental studies

    Science.gov (United States)

    Dai, J.; Belomestnykh, S.; Ben-Zvi, I.; Xu, Wencan

    2013-11-01

    We propose a theoretical model based on network analysis to study the external quality factor (Q factor) of dual-feed coupling for superconducting radio-frequency (SRF) cavities. Specifically, we apply our model to the dual-feed 704 MHz half-cell SRF gun for Brookhaven National Laboratory's prototype Energy Recovery Linac (ERL). The calculations show that the external Q factor of this dual-feed system is adjustable from 104 to 109 provided that the adjustment range of a phase shifter covers 0°-360°. With a period of 360°, the external Q factor of the coupling system changes periodically with the phase difference between the two coupling arms. When the RF phase of both coupling arms is adjusted simultaneously in the same direction, the external Q factor of the system also changes periodically, but with a period of 180°.

  10. Comparison of coal/solid recovered fuel (SRF) with coal/refuse derived fuel (RDF) in a fluidised bed reactor

    International Nuclear Information System (INIS)

    Wagland, S.T.; Kilgallon, P.; Coveney, R.; Garg, A.; Smith, R.; Longhurst, P.J.; Pollard, S.J.T.; Simms, N.

    2011-01-01

    An experimental study was undertaken to compare the differences between municipal solid waste (MSW) derived solid recovered fuel (SRF) (complying with CEN standards) and refuse derived fuel (RDF). Both fuels were co-combusted with coal in a 50 kW fluidised bed combustor and the metal emissions were compared. Synthetic SRF was prepared in the laboratory by grinding major constituents of MSW such as paper, plastic, textile and wood. RDF was obtained from a local mechanical treatment plant. Heavy metal emissions in flue gas and ash samples from the (coal + 10% SRF) fuel mixture were found to be within the acceptable range and were generally lower than that obtained for coal + 10% RDF fuel mixture. The relative distribution of heavy metals in ash components and the flue gas stream shows the presence of a large fraction (up to 98%) of most of the metals in the ash (except Hg and As). Thermo-gravimetric (TG) analysis of SRF constituents was performed to understand the behaviour of fuel mixtures in the absence and presence of air. The results obtained from the experimental study will enhance the confidence of fuel users towards using MSW-derived SRF as an alternative fuel.

  11. Spectroscopic properties of Er3+ and Yb3+ co-doped glass ceramics containing SrF2 nanocrystals

    International Nuclear Information System (INIS)

    Qiao Xvsheng; Fan Xianping; Wang Minquan; Zhang Xianghua

    2009-01-01

    The spectroscopic properties of Er 3+ /Yb 3+ co-doped 50SiO 2 -10Al 2 O 3 -20ZnF 2 -20SrF 2 glass and glass ceramic containing SrF 2 nanocrystals were investigated. The formation of SrF 2 nanocrystals in the glass ceramic was confirmed by XRD. The oscillator strengths for several transitions of the Er 3+ ions in the glass ceramic have been obtained and the Judd-Ofelt parameters were then determined. The XRD result and Judd-Ofelt parameters suggested that Er 3+ and Yb 3+ ions had efficiently enriched in the SrF 2 nanocrystals in the glass ceramic. The lifetime of excited states has been used to reveal the surroundings of luminescent Er 3+ and Yb 3+ and energy transfer (ET) mechanism between Er 3+ and Yb 3+ . Much stronger upconversion luminescence and longer lifetime of the Er 3+ /Yb 3+ co-doped glass ceramic were observed in comparison with the Er 3+ /Yb 3+ co-doped glass, which could be ascribed to more efficient ET from Yb 3+ to Er 3+ due to the enrichment of Yb 3+ and Er 3+ and the shortening of the distance between lanthanide ions in the precipitated SrF 2 nanocrystals.

  12. Niobium superconducting rf cavity fabrication by electrohydraulic forming

    CERN Document Server

    Cantergiani, E.; Léaux, F.; Perez Fontenla, A.T.; Prunet, S.; Dufay-Chanat, L.; Koettig, T.; Bertinelli, F.; Capatina, O.; Favre, G.; Gerigk, F.; Jeanson, A. C.; Fuzeau, J.; Avrillaud, G.; Alleman, D.; Bonafe, J.; Marty, P.

    2016-01-01

    Superconducting rf (SRF) cavities are traditionally fabricated from superconducting material sheets or made of copper coated with superconducting material, followed by trim machining and electron-beam welding. An alternative technique to traditional shaping methods, such as deep-drawing and spinning, is electrohydraulicforming (EHF). InEHF, half-cells areobtainedthrough ultrahigh-speed deformation ofblank sheets, using shockwaves induced in water by a pulsed electrical discharge. With respect to traditional methods, such a highly dynamic process can yield interesting results in terms of effectiveness, repeatability, final shape precision, higher formability, and reduced springback. In this paper, the first results of EHFon high purity niobium are presented and discussed. The simulations performed in order to master the multiphysics phenomena of EHF and to adjust its process parameters are presented. The microstructures of niobium half- cells produced by EHFand by spinning have been compared in terms of damage...

  13. Improved reactor cavity

    International Nuclear Information System (INIS)

    Katz, L.R.; Demarchais, W.E.

    1984-01-01

    A reactor pressure vessel disposed in a cavity has coolant inlet or outlet pipes extending through passages in the cavity walls and welded to pressure nozzles. The cavity wall has means for directing fluid away from a break at a weld away from the pressure vessel, and means for inhibiting flow of fluid toward the vessel. (author)

  14. Secondary Electron Emission from Plasma Processed Accelerating Cavity Grade Niobium

    Energy Technology Data Exchange (ETDEWEB)

    Basovic, Milos [Old Dominion Univ., Norfolk, VA (United States)

    2016-05-01

    by different techniques. Specifically, this work provides the results of SEY from the plasma cleaned cavity grade niobium (Nb) samples. Pure niobium is currently the material of choice for the fabrication of Superconducting Radio Frequency (SRF) cavities. The effect of plasma processing with two different gases will be examined in two groups of samples. The first group of samples is made from cavity grade niobium. The second group of samples is made from the same material, but include a welded joint made by electron beam welding, since in niobium SRF cavities the peak electric and magnetic field are seen in close proximity to the welded joints. Both groups of samples will be exposed to nitrogen (N2) and a mixture of argon with oxygen (Ar/O2) plasma. It is the goal of this research to determine the SEY on these two groups of samples before and after plasma processing as a function of the energy of primary electrons. The SEY as a function of the angle of incidence of the primary electrons is tested on the samples treated with Ar/O2 plasma.

  15. Secondary electron emission from plasma processed accelerating cavity grade niobium

    Science.gov (United States)

    Basovic, Milos

    by different techniques. Specifically, this work provides the results of SEY from the plasma cleaned cavity grade niobium (Nb) samples. Pure niobium is currently the material of choice for the fabrication of Superconducting Radio Frequency (SRF) cavities. The effect of plasma processing with two different gases will be examined in two groups of samples. The first group of samples is made from cavity grade niobium. The second group of samples is made from the same material, but include a welded joint made by electron beam welding, since in niobium SRF cavities the peak electric and magnetic field are seen in close proximity to the welded joints. Both groups of samples will be exposed to nitrogen (N2) and a mixture of argon with oxygen (Ar/O2) plasma. It is the goal of this research to determine the SEY on these two groups of samples before and after plasma processing as a function of the energy of primary electrons. The SEY as a function of the angle of incidence of the primary electrons is tested on the samples treated with Ar/O2 plasma.

  16. Laser excited fluorescence spectrum of Ho3+:SrF2 single crystal

    International Nuclear Information System (INIS)

    Lal, Bansi; Ramachandra Rao, D.

    1980-01-01

    The fluorescence spectrum of Ho 3+ : SrF 2 single crystal excited by the various lines of an Ar + laser, is reported. The three fluorescence groups recorded in the region 5300-7700 A, correspond to the transitions from ( 5 F 4 , 5 S 2 ) to 5 I 8 , 5 F 5 to 5 I 8 , 5 F 3 to 5 I 7 and ( 5 F 4 , 5 S 2 ) to 5 I 7 . Marked changes in the total integrated intensity of the various fluorescence groups with the change in the exciting wavelength are observed. (author)

  17. Study of thermal interaction between a 150 kW CW power coupler and a superconducting 704 MHz elliptical cavity

    Energy Technology Data Exchange (ETDEWEB)

    Souli, M. [Institut de Physique Nucleaire d' Orsay, CNRS/IN2P3, Orsay (France)]. E-mail: souli@ipno.in2p3.fr; Fouaidy, M. [Institut de Physique Nucleaire d' Orsay, CNRS/IN2P3, Orsay (France); Saugnac, H. [Institut de Physique Nucleaire d' Orsay, CNRS/IN2P3, Orsay (France); Szott, P. [Institut de Physique Nucleaire d' Orsay, CNRS/IN2P3, Orsay (France); Gandolfo, N. [Institut de Physique Nucleaire d' Orsay, CNRS/IN2P3, Orsay (France); Bousson, S. [Institut de Physique Nucleaire d' Orsay, CNRS/IN2P3, Orsay (France); Braud, D. [CEA Saclay, DSM/DAPNIA/SACM, 91191 Gif sur Yvette (France); Charrier, J.P. [CEA Saclay, DSM/DAPNIA/SACM, 91191 Gif sur Yvette (France); Roudier, D. [CEA Saclay, DSM/DAPNIA/SACM, 91191 Gif sur Yvette (France); Sahuquet, P. [CEA Saclay, DSM/DAPNIA/SACM, 91191 Gif sur Yvette (France); Visentin, B. [CEA Saclay, DSM/DAPNIA/SACM, 91191 Gif sur Yvette (France)

    2006-07-15

    The power coupler needed for {beta} = 0.65 SRF elliptical cavities dedicated to the driver of XADS (eXperimental Accelerator Driven System) should transmit a CW RF power of 150 kW to a 10 mA proton beam. The estimated average values of the RF losses in the coupler are 130 W (respectively 46 W) for the inner (respectively outer) conductor in SW mode. Due to such high values of the RF losses, it is necessary to very carefully design and optimize the cooling circuits of the coupler in order to efficiently remove the generated heat and to reduce the thermal load to the cavity operating at T = 2 K. An experiment simulating the thermal interaction between the power coupler and a 704 MHz SRF five cells cavity was performed in the CRYHOLAB test facility in order to determine the critical heat load that can be sustained by the cavity without degradation of its RF performance. Experimental data are compared to numerical simulation results obtained with the Finite Element Method code COSMOS/M. These data allow us also to perform in situ measurements of the thermal parameters needed in the thermal model of the coupler (thermal conductivity, thermal contact resistance). These data are used to validate numerical simulations.

  18. Performance of a reentrant cavity beam position monitor

    Directory of Open Access Journals (Sweden)

    Claire Simon

    2008-08-01

    Full Text Available The beam-based alignment and feedback systems, essential operations for the future colliders, require high resolution beam position monitors (BPMs. In the framework of the European CARE/SRF program, a reentrant cavity BPM with its associated electronics was developed by the CEA/DSM/Irfu in collaboration with DESY. The design, the fabrication, and the beam test of this monitor are detailed within this paper. This BPM is designed to be inserted in a cryomodule, work at cryogenic temperature in a clean environment. It has achieved a resolution better than 10  μm and has the possibility to perform bunch to bunch measurements for the x-ray free electron laser (X-FEL and the International Linear Collider (ILC. Its other features are a small size of the rf cavity, a large aperture (78 mm, and an excellent linearity. A first prototype of a reentrant cavity BPM was installed in the free electron laser in Hamburg (FLASH, at Deutsches Elektronen-Synchrotron (DESY and demonstrated its operation at cryogenic temperature inside a cryomodule. The second, installed, also, in the FLASH linac to be tested with beam, measured a resolution of approximately 4  μm over a dynamic range ±5  mm in single bunch.

  19. Performance of a reentrant cavity beam position monitor

    International Nuclear Information System (INIS)

    Simon, C.; Luong, M.; Chel, S.; Napoly, O.; Novo, J.; Roudier, D.; Rouviere, N.; Baboi, N.; Mildner, N.; Nolle, D.

    2008-01-01

    The beam-based alignment and feedback systems, essential operations for the future colliders, require high resolution beam position monitors (BPMs). In the framework of the European CARE/SRF program, a reentrant cavity BPM with its associated electronics was developed by the CEA/DSM/Irfu in collaboration with DESY. The design, the fabrication, and the beam test of this monitor are detailed within this paper. This BPM is designed to be inserted in a cryo-module, work at cryogenic temperature in a clean environment. It has achieved a resolution better than 10 μm and has the possibility to perform bunch to bunch measurements for the X-ray free electron laser (X-FEL) and the International Linear Collider (ILC). Its other features are a small size of the rf cavity, a large aperture (78 mm), and an excellent linearity. A first prototype of a reentrant cavity BPM was installed in the free electron laser in Hamburg (FLASH), at Deutsches Elektronen-Synchrotron (DESY) and demonstrated its operation at cryogenic temperature inside a cryo-module. The second, installed, also, in the FLASH linac to be tested with beam, measured a resolution of approximately 4 μm over a dynamic range ± 5 mm in single bunch. (authors)

  20. Performance of a reentrant cavity beam position monitor

    Science.gov (United States)

    Simon, Claire; Luong, Michel; Chel, Stéphane; Napoly, Olivier; Novo, Jorge; Roudier, Dominique; Rouvière, Nelly; Baboi, Nicoleta; Mildner, Nils; Nölle, Dirk

    2008-08-01

    The beam-based alignment and feedback systems, essential operations for the future colliders, require high resolution beam position monitors (BPMs). In the framework of the European CARE/SRF program, a reentrant cavity BPM with its associated electronics was developed by the CEA/DSM/Irfu in collaboration with DESY. The design, the fabrication, and the beam test of this monitor are detailed within this paper. This BPM is designed to be inserted in a cryomodule, work at cryogenic temperature in a clean environment. It has achieved a resolution better than 10μm and has the possibility to perform bunch to bunch measurements for the x-ray free electron laser (X-FEL) and the International Linear Collider (ILC). Its other features are a small size of the rf cavity, a large aperture (78 mm), and an excellent linearity. A first prototype of a reentrant cavity BPM was installed in the free electron laser in Hamburg (FLASH), at Deutsches Elektronen-Synchrotron (DESY) and demonstrated its operation at cryogenic temperature inside a cryomodule. The second, installed, also, in the FLASH linac to be tested with beam, measured a resolution of approximately 4μm over a dynamic range ±5mm in single bunch.

  1. Effect of low temperature baking on the RF properties of niobium superconducting cavities for particle accelerators

    International Nuclear Information System (INIS)

    Gianluigi Ciovati

    2004-01-01

    Radio-frequency superconducting (SRF) cavities are widely used to accelerate a charged particle beam in particle accelerators. The performance of SRF cavities made of bulk niobium has significantly improved over the last ten years and is approaching the theoretical limit for niobium. Nevertheless, RF tests of niobium cavities are still showing some ''anomalous'' losses that require a better understanding in order to reliably obtain better performance. These losses are characterized by a marked dependence of the surface resistance on the surface electromagnetic field and can be detected by measuring the quality factor of the resonator as a function of the peak surface field. A low temperature (100 C-150 C) ''in situ'' bake under ultra-high vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor at low field and a recovery from ''anomalous'' losses (so-called ''Q-drop'') without field emission at higher field. A series of experiments with a CEBAF single-cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37 K-280 K and resonant frequency shift between 6 K-9.3 K provide information about the surface resistance, energy gap, penetration depth and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity. The hydrogen content of small niobium samples inserted in the cavity during its surface preparation was analyzed with Nuclear Reaction Analysis (NRA). The single-cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models

  2. Exploring the Physics Limitations of Compact High Gradient Accelerating Structures Simulations of the Electron Current Spectrometer Setup in Geant4

    CERN Document Server

    Van Vliet, Philine Julia

    2017-01-01

    The high field gradient of 100 MV/m that will be applied to the accelerator cavities of the Compact Linear Collider (CLIC), gives rise to the problem of RF breakdowns. The field collapses and a plasma of electrons and ions is being formed in the cavity, preventing the RF field from penetrating the cavity. Electrons in the plasma are being accelerated and ejected out, resulting in a breakdown current up to a few Amp`eres, measured outside the cavities. These breakdowns lead to luminosity loss, so reducing their amount is of great importance. For this, a better understanding of the physics behind RF breakdowns is needed. To study these breakdowns, the XBox 2 test facility has a spectrometer setup installed after the RF cavity that is being conditioned. For this report, a simulation of this spectrometer setup has been made using Geant4. Once a detailed simulation of the RF field and cavity has been made, it can be connected to this simulation of the spectrometer setup and used to recreate the data that has b...

  3. Oncogenic N-Ras Stimulates SRF-Mediated Transactivation via H3 Acetylation at Lysine 9

    Directory of Open Access Journals (Sweden)

    Sun-Ju Yi

    2018-01-01

    Full Text Available Signal transduction pathways regulate the gene expression by altering chromatin dynamics in response to mitogens. Ras proteins are key regulators linking extracellular stimuli to a diverse range of biological responses associated with gene regulation. In mammals, the three ras genes encode four Ras protein isoforms: H-Ras, K-Ras4A, K-Ras4B, and N-Ras. Although emerging evidence suggests that Ras isoforms differentially regulate gene expressions and are functionally nonredundant, the mechanisms underlying Ras specificity and Ras signaling effects on gene expression remain unclear. Here, we show that oncogenic N-Ras acts as the most potent regulator of SRF-, NF-κB-, and AP-1-dependent transcription. N-Ras-RGL2 axis is a distinct signaling pathway for SRF target gene expression such as Egr1 and JunB, as RGL2 Ras binding domain (RBD significantly impaired oncogenic N-Ras-induced SRE activation. By monitoring the effect of Ras isoforms upon the change of global histone modifications in oncogenic Ras-overexpressed cells, we discovered that oncogenic N-Ras elevates H3K9ac/H3K23ac levels globally in the chromatin context. Importantly, chromatin immunoprecipitation (ChIP assays revealed that H3K9ac is significantly enriched at the promoter and coding regions of Egr1 and JunB. Collectively, our findings define an undocumented role of N-Ras in modulating of H3 acetylation and in gene regulation.

  4. Heat load of a GaAs photocathode in an SRF electron gun

    International Nuclear Information System (INIS)

    Wang Erdong; Zhao Kui; Jorg Kewisch; Ilan Ben-Zvi; Andrew Burrill; Trivini Rao; Wu Qiong; Animesh Jain; Ramesh Gupta; Doug Holmes

    2011-01-01

    A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved by using a superconducting radio frequency (SRF) electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide (GaAs) photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder (plug) to decrease the heat load from GaAs. (authors)

  5. Current state of X-band accelerating structure high gradient test. Be held at high energy accelerator organization on April 15, 2005

    International Nuclear Information System (INIS)

    Watanabe, Ken; Higo, Toshiyasu

    2005-01-01

    XTF (X-band Test Facility, Old name is GLCTA) is the high gradient test facility for X-band acceleration. We have installed an X-band 60cm structure (KX01) in the April 2004 and have been processing it for more than 10 months. Now it is under test on long-term operation. We report here the high gradient test result to date. (author)

  6. Production of Seamless Superconducting Radio Frequency Cavities from Ultra-fine Grained Niobium, Phase II Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Roy Crooks, Ph.D., P.E.

    2009-10-31

    The positron and electron linacs of the International Linear Collider (ILC) will require over 14,000, nine-cell, one meter length, superconducting radio frequency (SRF) cavities [ILC Reference Design Report, 2007]. Manufacturing on this scale will benefit from more efficient fabrication methods. The current methods of fabricating SRF cavities involve deep drawing of the halves of each of the elliptical cells and joining them by high-vacuum, electron beam welding, with at least 19 circumferential welds per cavity. The welding is costly and has undesirable effects on the cavity surfaces, including grain-scale surface roughening at the weld seams. Hydroforming of seamless tubes avoids welding, but hydroforming of coarse-grained seamless tubes results in strain-induced surface roughening. Surface roughness limits accelerating fields, because asperities prematurely exceed the critical magnetic field and become normal conducting. This project explored the technical and economic feasibility of an improved processing method for seamless tubes for hydroforming. Severe deformation of bulk material was first used to produce a fine structure, followed by extrusion and flow-forming methods of tube making. Extrusion of the randomly oriented, fine-grained bulk material proceeded under largely steady-state conditions, and resulted in a uniform structure, which was found to be finer and more crystallographically random than standard (high purity) RRR niobium sheet metal. A 165 mm diameter billet of RRR grade niobium was processed into five, 150 mm I.D. tubes, each over 1.8 m in length, to meet the dimensions used by the DESY ILC hydroforming machine. Mechanical properties met specifications. Costs of prototype tube production were approximately twice the price of RRR niobium sheet, and are expected to be comparable with economies of scale. Hydroforming and superconducting testing will be pursued in subsequent collaborations with DESY and Fermilab. SRF Cavities are used to construct

  7. Cryogenics for a vertical test stand facility for testing superconducting radio frequency cavities at RRCAT

    International Nuclear Information System (INIS)

    Gupta, Prabhat Kumar; Kumar, Manoj; Kush, P.K.

    2015-01-01

    Vertical Test Stand (VTS) Facility is located in a newly constructed building of Cryo-Engineering and Cryo-Module Development Division (CCDD). This test facility is one of the important facilities to develop SCRF technologies for superconducting accelerators like Indian Spallation Neutron Source. VTS has to be used for regular testing of the Superconducting Radio Frequency (SRF) Niobium cavities at nominal frequency of 1.3 GHz/ 650 MHz at 4 K / 2 K liquid helium (LHe) bath temperatures. Testing of these cavities at 2 K evaluates cavity processing methods, procedures and would also serve as a pre-qualification test for cavity to test it in horizontal cryostat, called horizontal test stand, with other cavity components such as tuner and helium vessel. Cryogenic technologies play a major role in these cavity testing facilities. Achieving and maintaining a stable temperature of 2 K in these test stands on regular and reliable basis is a challenging task and require broad range of cryogenic expertise, large scale system level understanding and many in-house technological and process developments. Furthermore this test stand will handle large amount of liquid helium. Therefore, an appropriately designed infrastructure is required to handle such large amount of helium gas generated during the operation of VTS .This paper describes the different cryogenic design aspects, initial cryogenic operation results and different cryogenic safety aspects. (author)

  8. Proceedings of the PILAC cavity review, May 15, 1992

    International Nuclear Information System (INIS)

    1992-01-01

    This is a proposal for the third year of conception and preliminary technical analysis of the superconducting cavities for a pion linear accelerator which would be capable of achieving the high-flux (10 9 pions/sec), high-resolution (2 parts in 10 4 , 2000 keV) (920 MeV pion kinetic energy) requirements needed for future basic research opportunities set forth by the nuclear physics scientific community. The scope of the proposal includes experiments and analysis directed at ''proof of principle'' to achieve these performance goals. Central to this effort is advanced study and tests of new concepts which could provide high-gradient superconducting RF cavities to accelerate pions rapidly before significant losses are incurred due to the decay of these short-lived particles

  9. The LHC superconducting cavities

    CERN Document Server

    Boussard, Daniel; Häbel, E; Kindermann, H P; Losito, R; Marque, S; Rödel, V; Stirbet, M

    1999-01-01

    The LHC RF system, which must handle high intensity (0.5 A d.c.) beams, makes use of superconducting single-cell cavities, best suited to minimizing the effects of periodic transient beam loading. There will be eight cavities per beam, each capable of delivering 2 MV (5 MV/m accelerating field) at 400 MHz. The cavities themselves are now being manufactured by industry, using niobium-on-copper technology which gives full satisfaction at LEP. A cavity unit includes a helium tank (4.5 K operating temperature) built around a cavity cell, RF and HOM couplers and a mechanical tuner, all housed in a modular cryostat. Four-unit modules are ultimately foreseen for the LHC (two per beam), while at present a prototype version with two complete units is being extensively tested. In addition to a detailed description of the cavity and its ancillary equipment, the first test results of the prototype will be reported.

  10. LEP copper accelerating cavities

    CERN Multimedia

    Laurent Guiraud

    1999-01-01

    These copper cavities were used to generate the radio frequency electric field that was used to accelerate electrons and positrons around the 27-km Large Electron-Positron (LEP) collider at CERN, which ran from 1989 to 2000. The copper cavities were gradually replaced from 1996 with new superconducting cavities allowing the collision energy to rise from 90 GeV to 200 GeV by mid-1999.

  11. Reduction of field emission in superconducting cavities with high power pulsed RF

    International Nuclear Information System (INIS)

    Graber, J.; Crawford, C.; Kirchgessner, J.; Padamsee, H.; Rubin, D.; Schmueser, P.

    1994-01-01

    A systematic study is presented of the effects of pulsed high power RF processing (HPP) as a method of reducing field emission (FE) in superconducting radio frequency (SRF) cavities to reach higher accelerating gradients for future particle accelerators. The processing apparatus was built to provide up to 150 kW peak RF power to 3 GHz cavities, for pulse lengths from 200 μs to 1 ms. Single-cell and nine-cell cavities were tested extensively. The thermal conductivity of the niobium for these cavities was made as high as possible to ensure stability against thermal breakdown of superconductivity. HPP proves to be a highly successful method of reducing FE loading in nine-cell SRF cavities. Attainable continuous wave (CW) fields increase by as much as 80% from their pre-HPP limits. The CW accelerating field achieved with nine-cell cavities improved from 8-15 MV/m with HPP to 14-20 MV/m. The benefits are stable with subsequent exposure to dust-free air. More importantly, HPP also proves effective against new field emission subsequently introduced by cold and warm vacuum ''accidents'' which admitted ''dirty'' air into the cavities. Clear correlations are obtained linking FE reduction with the maximum surface electric field attained during processing. In single cells the maximums reached were E peak =72 MV/m and H peak =1660 Oe. Thermal breakdown, initiated by accompanying high surface magnetic fields is the dominant limitation on the attainable fields for pulsed processing, as well as for final CW and long pulse operation. To prove that the surface magnetic field rather than the surface electric fields is the limitation to HPP effectiveness, a special two-cell cavity with a reduced magnetic to electric field ratio is successfully tested. During HPP, pulsed fields reach E peak =113 MV/m (H peak =1600 Oe) and subsequent CW low power measurement reached E peak =100 MV/m, the highest CW field ever measured in a superconducting accelerator cavity. ((orig.))

  12. Experimental Study of the Effect of Beam Loading on RF Breakdown Rate in CLIC High-Gradient Accelerating Structures

    CERN Document Server

    Tecker, F; Kelisani, M; Doebert, S; Grudiev, A; Quirante, J; Riddone, G; Syratchev, I; Wuensch, W; Kononenko, O; Solodko, A; Lebet, S

    2013-01-01

    RF breakdown is a key issue for the multi-TeV highluminosity e+e- Compact Linear Collider (CLIC). Breakdowns in the high-gradient accelerator structures can deflect the beam and decrease the desired luminosity. The limitations of the accelerating structures due to breakdowns have been studied so far without a beam present in the structure. The presence of the beam modifies the distribution of the electrical and magnetic field distributions, which determine the breakdown rate. Therefore an experiment has been designed for high power testing a CLIC prototype accelerating structure with a beam present in the CLIC Test Facility (CTF3). A special beam line allows extracting a beam with nominal CLIC beam current and duration from the CTF3 linac. The paper describes the beam optics design for this experimental beam line and the commissioning of the experiment with beam.

  13. The Role of CREB, SRF, and MEF2 in Activity-Dependent Neuronal Plasticity in the Visual Cortex.

    Science.gov (United States)

    Pulimood, Nisha S; Rodrigues, Wandilson Dos Santos; Atkinson, Devon A; Mooney, Sandra M; Medina, Alexandre E

    2017-07-12

    The transcription factors CREB (cAMP response element binding factor), SRF (serum response factor), and MEF2 (myocyte enhancer factor 2) play critical roles in the mechanisms underlying neuronal plasticity. However, the role of the activation of these transcription factors in the different components of plasticity in vivo is not well known. In this study, we tested the role of CREB, SRF, and MEF2 in ocular dominance plasticity (ODP), a paradigm of activity-dependent neuronal plasticity in the visual cortex. These three proteins bind to the synaptic activity response element (SARE), an enhancer sequence found upstream of many plasticity-related genes (Kawashima et al., 2009; Rodríguez-Tornos et al., 2013), and can act cooperatively to express Arc , a gene required for ODP (McCurry et al., 2010). We used viral-mediated gene transfer to block the transcription function of CREB, SRF, and MEF2 in the visual cortex, and measured visually evoked potentials in awake male and female mice before and after a 7 d monocular deprivation, which allowed us to examine both the depression component (Dc-ODP) and potentiation component (Pc-ODP) of plasticity independently. We found that CREB, SRF, and MEF2 are all required for ODP, but have differential effects on Dc-ODP and Pc-ODP. CREB is necessary for both Dc-ODP and Pc-ODP, whereas SRF and MEF2 are only needed for Dc-ODP. This finding supports previous reports implicating SRF and MEF2 in long-term depression (required for Dc-ODP), and CREB in long-term potentiation (required for Pc-ODP). SIGNIFICANCE STATEMENT Activity-dependent neuronal plasticity is the cellular basis for learning and memory, and it is crucial for the refinement of neuronal circuits during development. Identifying the mechanisms of activity-dependent neuronal plasticity is crucial to finding therapeutic interventions in the myriad of disorders where it is disrupted, such as Fragile X syndrome, Rett syndrome, epilepsy, major depressive disorder, and autism

  14. Biased HiPIMS technology for superconducting rf accelerating cavities coating

    CERN Document Server

    G. Rosaz, G.; Sonato, D.; Calatroni, S.; Ehiasarian, A.; Junginger, T.; Taborelli, M.

    2016-01-01

    In the last few years the interest of the thin film science and technology community on High Impulse Power Magnetron Sputtering (HIPIMS) coatings has steadily increased. HIPIMS literature shows that better thin film morphology, denser and smoother films can be achieved when compared with standard dc Magnetron Sputtering (dcMS) coating technology. Furthermore the capability of HIPIMS to produce a high quantity of ionized species can allow conformal coatings also for complex geometries. CERN already studied the possibility to use such a coating method for SRF accelerating cavities. Results are promising but not better from a RF point of view than dcMS coatings. Thanks to these results the next step is to go towards a biased HiPIMS approach. However the geometry of the cavities leads to complex changes in the coating setup in order to apply a bias voltage. Coating system tweaking and first superconducting properties of biased samples are presented.

  15. Design approach for the development of a cryomodule for compact crab cavities for Hi-Lumi LHC

    Science.gov (United States)

    Pattalwar, Shrikant; Jones, Thomas; Templeton, Niklas; Goudket, Philippe; McIntosh, Peter; Wheelhouse, Alan; Burt, Graeme; Hall, Ben; Wright, Loren; Peterson, Tom

    2014-01-01

    A prototype Superconducting RF (SRF) cryomodule, comprising multiple compact crab cavities is foreseen to realise a local crab crossing scheme for the "Hi-Lumi LHC", a project launched by CERN to increase the luminosity performance of LHC. A cryomodule with two cavities will be initially installed and tested on the SPS drive accelerator at CERN to evaluate performance with high-intensity proton beams. A series of boundary conditions influence the design of the cryomodule prototype, arising from; the complexity of the cavity design, the requirement for multiple RF couplers, the close proximity to the second LHC beam pipe and the tight space constraints in the SPS and LHC tunnels. As a result, the design of the helium vessel and the cryomodule has become extremely challenging. This paper assesses some of the critical cryogenic and engineering design requirements and describes an optimised cryomodule solution for the evaluation tests on SPS.

  16. Etching of Niobium Sample Placed on Superconducting Radio Frequency Cavity Surface in Ar/CL2 Plasma

    International Nuclear Information System (INIS)

    Upadhyay, Janardan; Phillips, Larry; Valente, Anne-Marie

    2011-01-01

    Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. It has been proven with flat samples that the bulk Niobium (Nb) removal rate and the surface roughness after the plasma etchings are equal to or better than wet etching processes. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. The etching results will be presented at this conference.

  17. Etching of Niobium Sample Placed on Superconducting Radio Frequency Cavity Surface in Ar/CL2 Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Janardan Upadhyay, Larry Phillips, Anne-Marie Valente

    2011-09-01

    Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. It has been proven with flat samples that the bulk Niobium (Nb) removal rate and the surface roughness after the plasma etchings are equal to or better than wet etching processes. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. The etching results will be presented at this conference.

  18. Foundations for quantitative microstructural models to track evolution of the metallurgical state during high purity Nb cavity fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Bieler, Thomas R [Michigan State University; Wright, Neil T [Michigan State University; Compton, Chris C [Facility for Rare Isotope Beams

    2014-03-15

    The goal of the Materials Science SRF Cavity Group of Michigan State University and the National Superconducting Cyclotron has been (and continues to be) to understand quantitatively the effects of process history on functional properties. These relationships were assessed via studies on Nb samples and cavity parts, which had various combinations of forming processes, welding, heat treatments, and surface preparation. A primary focus was on large-grain cavity building strategies. Effects of processing operations and exposure to hydrogen on the thermal conductivity has been identified in single and bi-crystal samples, showing that the thermal conductivity can be altered by a factor of 5 depending on process history. Characterization of single crystal tensile samples show a strong effect of crystal orientation on deformation resistance and shape changes. Large grain half cells were examined to characterize defect content and surface damage effects, which provided quantitative information about the depth damage layers from forming.

  19. Suppression of hydride precipitates in niobium superconducting radio-frequency cavities

    Science.gov (United States)

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-10-01

    Niobium hydride is a suspected contributor to degraded niobium superconducting radio-frequency (SRF) cavity performance by Q slope and Q disease. The concentration and distribution of hydrogen atoms in niobium can be strongly affected by the cavity processing treatments. This study provides guidance for cavity processing based on density functional theory calculations of the properties of common processing impurity species—hydrogen, oxygen, nitrogen, and carbon—in the body-centered cubic (bcc) niobium lattice. We demonstrate that some fundamental properties are shared between the impurity atoms, such as anionic character in niobium. The strain field produced, however, by hydrogen atoms is both geometrically different and substantially weaker than the strain field produced by the other impurities. We focus on the interaction between oxygen and hydrogen atoms in the lattice, and demonstrate that the elastic interactions between these species and the bcc niobium lattice cause trapping of hydrogen and oxygen atoms by bcc niobium lattice vacancies. We also show that the attraction of oxygen to a lattice vacancy is substantially stronger than the attraction of hydrogen to the vacancy. Additionally, hydrogen dissolved in niobium tetrahedral interstitial sites can be trapped by oxygen, nitrogen and possibly carbon atoms dissolved in octahedral interstitial sites. These results indicate that the concentration of oxygen in the bcc lattice can have a strong impact on the ability of hydrogen to form detrimental phases. Based on our results and a literature survey, we propose a mechanism for the success of the low-temperature annealing step applied to niobium SRF cavities. We also recommend further examination of nitrogen and carbon in bcc niobium, and particularly the role that nitrogen can play in preventing detrimental hydride phase formation.

  20. Development of a high brightness, high current SRF photo-electron source for ERL applications

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Axel [Helmholtz-Zentrum Berlin (Germany); Collaboration: bERLinPro Team

    2016-07-01

    Energy recovery linacs (ERL) offer the potential to combine major beam properties of the two main domains of particle accelerators: The low emittance of linear accelerators and the high average beam current of storage rings, while also allowing to compress to short bunches below the ps regime. This makes among other applications ERLs an ideal candidate for future light sources. The beam properties of the ERL are given by the performance of the injection section and hence of the beam source. Helmholtz-Zentrum Berlin is currently designing and building a high average current all superconducting CW driven ERL as a prototype to demonstrate low normalized beam emittance of 1 mm*mrad at 100 mA and short pulses of about 2 ps. In this contribution we discuss the development of this class of a high brightness, high current SRF photo-electron source and present recent commissioning results. Also, alternative approaches at other laboratories are shortly reviewed.

  1. SRF Accelerator Technology Transfer Experience from the Achievement of the SNS Cryomodule Production Run

    CERN Document Server

    Hogan, John; Daly, Edward; Drury, Michael A; Fischer, John; Hiatt, Tommy; Kneisel, Peter; Mammosser, John; Preble, Joseph P; Whitlatch, Timothy; Wilson, Katherine; Wiseman, Mark

    2005-01-01

    This paper will discuss the technology transfer aspect of superconducting RF expertise, as it pertains to cryomodule production, beginning with the original design requirements through testing and concluding with product delivery to the end user. The success of future industrialization, of accelerator systems, is dependent upon a focused effort on accelerator technology transfer. Over the past twenty years the Thomas Jefferson National Accelerator Facility (Jefferson Lab) has worked with industry to successfully design, manufacture, test and commission more superconducting RF cryomodules than any other entity in the United States. The most recent accomplishment of Jefferson Lab has been the successful production of twenty-four cryomodules designed for the Spallation Neutron Source (SNS). Jefferson Lab was chosen, by the United States Department of Energy, to provide the superconducting portion of the SNS linac due to its reputation as a primary resource for SRF expertise. The successful partnering with, and d...

  2. Cavity design programs

    International Nuclear Information System (INIS)

    Nelson, E.M.

    1996-01-01

    Numerous computer programs are available to help accelerator physicists and engineers model and design accelerator cavities and other microwave components. This article discusses the problems these programs solve and the principles upon which these programs are based. Some examples of how these programs are used in the design of accelerator cavities are also given

  3. Cavity quantum electrodynamics

    International Nuclear Information System (INIS)

    Walther, Herbert; Varcoe, Benjamin T H; Englert, Berthold-Georg; Becker, Thomas

    2006-01-01

    This paper reviews the work on cavity quantum electrodynamics of free atoms. In recent years, cavity experiments have also been conducted on a variety of solid-state systems resulting in many interesting applications, of which microlasers, photon bandgap structures and quantum dot structures in cavities are outstanding examples. Although these phenomena and systems are very interesting, discussion is limited here to free atoms and mostly single atoms because these systems exhibit clean quantum phenomena and are not disturbed by a variety of other effects. At the centre of our review is the work on the one-atom maser, but we also give a survey of the entire field, using free atoms in order to show the large variety of problems dealt with. The cavity interaction can be separated into two main regimes: the weak coupling in cavity or cavity-like structures with low quality factors Q and the strong coupling when high-Q cavities are involved. The weak coupling leads to modification of spontaneous transitions and level shifts, whereas the strong coupling enables one to observe a periodic exchange of photons between atoms and the radiation field. In this case, atoms and photons are entangled, this being the basis for a variety of phenomena observed, some of them leading to interesting applications in quantum information processing. The cavity experiments with free atoms reached a new domain with the advent of experiments in the visible spectral region. A review on recent achievements in this area is also given

  4. Formation of coronal cavities

    International Nuclear Information System (INIS)

    An, C.H.; Suess, S.T.; Tandberg-Hanssen, E.; Steinolfson, R.S.

    1986-01-01

    A theoretical study of the formation of a coronal cavity and its relation to a quiescent prominence is presented. It is argued that the formation of a cavity is initiated by the condensation of plasma which is trapped by the coronal magnetic field in a closed streamer and which then flows down to the chromosphere along the field lines due to lack of stable magnetic support against gravity. The existence of a coronal cavity depends on the coronal magnetic field strength; with low strength, the plasma density is not high enough for condensation to occur. Furthermore, we suggest that prominence and cavity material is supplied from the chromospheric level. Whether a coronal cavity and a prominence coexist depends on the magnetic field configuration; a prominence requires stable magnetic support

  5. High gradient magnetic separation

    International Nuclear Information System (INIS)

    Prothero, D.H.

    1982-01-01

    In a process in which magnetic material is trapped in a filter disposed in a magnetic field, and is unloaded by passing a fluid through the filter in the absence of the initial magnetic field, the magnetic field is first reduced to an intermediate value to allow unloading of the more weakly magnetic particles, the more strongly magnetic particles being retained and subsequently unloaded by further reduction of the magnetic field. Stage by stage reduction of the magnetic field during unloading allows separation of different species from the mixture. As an example the method can be applied to the separation of uranium compounds from mine ores. The uranium compounds are magnetic, while most of the other constituents of the ore are non-magnetic. The starting material is a suspension of the ore. Water is used for unloading. The filter material in this case is stainless steel balls. (author)

  6. CLIC crab cavity final report

    CERN Document Server

    Burt, G et al

    2013-01-01

    A high gradient 12 GHz, normal‐conducting travelling‐wave structure, with a high group‐velocity to minimise the effects of beam loading, has been developed. Appropriate input coupler and wakefield damping processes have been incorporated and two ‘undamped’ structures have been fabricated, one in the UK by Shakespeare Engineering Ltd and the other by VDL at CERN. Systematic high gradient tests are planned at SLAC and CERN, to study breakdown differences between deflecting and accelerating structures.

  7. Resonant-frequency discharge in a multi-cell radio frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Popovic, S; Upadhyay, J; Mammosser, J; Nikolic, M; Vuskovic, L

    2014-11-07

    We are reporting experimental results on microwave discharge operating at resonant frequency in a multi-cell radio frequency (RF) accelerator cavity. Although the discharge operated at room temperature, the setup was constructed so that it could be used for plasma generation and processing in fully assembled active superconducting radio-frequency (SRF) cryomodule (in situ operation). This discharge offers an efficient mechanism for removal of a variety of contaminants, organic or oxide layers, and residual particulates from the interior surface of RF cavities through the interaction of plasma-generated radicals with the cavity walls. We describe resonant RF breakdown conditions and address the problems related to generation and sustaining the multi-cell cavity plasma, which are breakdown and resonant detuning. We have determined breakdown conditions in the cavity, which was acting as a plasma vessel with distorted cylindrical geometry. We discuss the spectroscopic data taken during plasma removal of contaminants and use them to evaluate plasma parameters, characterize the process, and estimate the volatile contaminant product removal.

  8. The fundamental science of nitrogen-doping of niobium superconducting cavities

    Science.gov (United States)

    Gonnella, Daniel Alfred

    Doping of niobium superconducting RF cavities with impurities has been demonstrated to have the ability to significantly improve the cryogenic efficiency of the accelerating structures. Doping SRF cavities with nitrogen is a relatively simple additional step to cavity preparation that can make drastic improvements in a cavity's intrinsic quality factor, Q0. Nitrogen-doping consists of treating SRF cavities at high temperatures in a low nitrogen-atmosphere. This leads to two important effects: an improvement in Q0 at low fields, and the presence of an "anti-Q slope" in which the cryogenic efficiency of doped cavities actually improves at higher fields. After its initial discovery, nitrogen-doping showed real promise but many fundamental scientific questions remained about the process. Nitrogen-doped cavities consistently quenched at lower fields than un-doped cavities, cooling the cavities through their critical temperature slowly led to poor performance, and the mechanism behind the Q0 improvement was not well understood. This dissertation focuses on addressing these issues. Single-cell 1.3 GHz cavities were prepared with different nitrogen-dopings and their effects studied systematically. It was found that nitrogen-doping drastically lowers the mean free path of the RF penetration layer of the niobium, leading to a lowering of the temperature-dependent BCS resistance, RBCS, at low fields. Theoretical work to predict the anti-Q slope was compared with experimental results to more fundamentally understand the nature of the field dependence of RBCS. Nitrogen-doped cavities were found to have a much larger sensitivity of residual resistance from trapped magnetic flux than un-doped cavities. Fast cool downs with large spatial temperature gradients through Tc were found to more efficiently expel magnetic flux. The full dependence of this sensitivity to trapped magnetic flux was studied as a function of changing mean free path and found to be in good agreement with

  9. SPS RF Accelerating Cavity

    CERN Multimedia

    1979-01-01

    This picture shows one of the 2 new cavities installed in 1978-1979. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also increased: to the first 2 MW plant a second 2 MW plant was added and by end 1979 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412016X, 7412017X, 7411048X

  10. Superconducting TESLA cavities

    Directory of Open Access Journals (Sweden)

    B. Aune

    2000-09-01

    Full Text Available The conceptional design of the proposed linear electron-positron collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with an accelerating gradient of E_{acc}≥25 MV/m at a quality factor Q_{0}≥5×10^{9}. The design goal for the cavities of the TESLA Test Facility (TTF linac was set to the more moderate value of E_{acc}≥15 MV/m. In a first series of 27 industrially produced TTF cavities the average gradient at Q_{0}=5×10^{9} was measured to be 20.1±6.2 MV/m, excluding a few cavities suffering from serious fabrication or material defects. In the second production of 24 TTF cavities, additional quality control measures were introduced, in particular, an eddy-current scan to eliminate niobium sheets with foreign material inclusions and stringent prescriptions for carrying out the electron-beam welds. The average gradient of these cavities at Q_{0}=5×10^{9} amounts to 25.0±3.2 MV/m with the exception of one cavity suffering from a weld defect. Hence only a moderate improvement in production and preparation techniques will be needed to meet the ambitious TESLA goal with an adequate safety margin. In this paper we present a detailed description of the design, fabrication, and preparation of the TESLA Test Facility cavities and their associated components and report on cavity performance in test cryostats and with electron beam in the TTF linac. The ongoing research and development towards higher gradients is briefly addressed.

  11. Cavity-enhanced spectroscopies

    CERN Document Server

    van Zee, Roger

    2003-01-01

    ""Cavity-Enhanced Spectroscopy"" discusses the use of optical resonators and lasers to make sensitive spectroscopic measurements. This volume is written by the researcchers who pioneered these methods. The book reviews both the theory and practice behind these spectroscopic tools and discusses the scientific discoveries uncovered by these techniques. It begins with a chapter on the use of optical resonators for frequency stabilization of lasers, which is followed by in-depth chapters discussing cavity ring-down spectroscopy, frequency-modulated, cavity-enhanced spectroscopy, intracavity spectr

  12. Tuned optical cavity magnetometer

    Science.gov (United States)

    Okandan, Murat; Schwindt, Peter

    2010-11-02

    An atomic magnetometer is disclosed which utilizes an optical cavity formed from a grating and a mirror, with a vapor cell containing an alkali metal vapor located inside the optical cavity. Lasers are used to magnetically polarize the alkali metal vapor and to probe the vapor and generate a diffracted laser beam which can be used to sense a magnetic field. Electrostatic actuators can be used in the magnetometer for positioning of the mirror, or for modulation thereof. Another optical cavity can also be formed from the mirror and a second grating for sensing, adjusting, or stabilizing the position of the mirror.

  13. Hydroforming of elliptical cavities

    Science.gov (United States)

    Singer, W.; Singer, X.; Jelezov, I.; Kneisel, P.

    2015-02-01

    Activities of the past several years in developing the technique of forming seamless (weldless) cavity cells by hydroforming are summarized. An overview of the technique developed at DESY for the fabrication of single cells and multicells of the TESLA cavity shape is given and the major rf results are presented. The forming is performed by expanding a seamless tube with internal water pressure while simultaneously swaging it axially. Prior to the expansion the tube is necked at the iris area and at the ends. Tube radii and axial displacements are computer controlled during the forming process in accordance with results of finite element method simulations for necking and expansion using the experimentally obtained strain-stress relationship of tube material. In cooperation with industry different methods of niobium seamless tube production have been explored. The most appropriate and successful method is a combination of spinning or deep drawing with flow forming. Several single-cell niobium cavities of the 1.3 GHz TESLA shape were produced by hydroforming. They reached accelerating gradients Eacc up to 35 MV /m after buffered chemical polishing (BCP) and up to 42 MV /m after electropolishing (EP). More recent work concentrated on fabrication and testing of multicell and nine-cell cavities. Several seamless two- and three-cell units were explored. Accelerating gradients Eacc of 30 - 35 MV /m were measured after BCP and Eacc up to 40 MV /m were reached after EP. Nine-cell niobium cavities combining three three-cell units were completed at the company E. Zanon. These cavities reached accelerating gradients of Eacc=30 - 35 MV /m . One cavity is successfully integrated in an XFEL cryomodule and is used in the operation of the FLASH linear accelerator at DESY. Additionally the fabrication of bimetallic single-cell and multicell NbCu cavities by hydroforming was successfully developed. Several NbCu clad single-cell and double-cell cavities of the TESLA shape have been

  14. Hydroforming of elliptical cavities

    Directory of Open Access Journals (Sweden)

    W. Singer

    2015-02-01

    Full Text Available Activities of the past several years in developing the technique of forming seamless (weldless cavity cells by hydroforming are summarized. An overview of the technique developed at DESY for the fabrication of single cells and multicells of the TESLA cavity shape is given and the major rf results are presented. The forming is performed by expanding a seamless tube with internal water pressure while simultaneously swaging it axially. Prior to the expansion the tube is necked at the iris area and at the ends. Tube radii and axial displacements are computer controlled during the forming process in accordance with results of finite element method simulations for necking and expansion using the experimentally obtained strain-stress relationship of tube material. In cooperation with industry different methods of niobium seamless tube production have been explored. The most appropriate and successful method is a combination of spinning or deep drawing with flow forming. Several single-cell niobium cavities of the 1.3 GHz TESLA shape were produced by hydroforming. They reached accelerating gradients E_{acc} up to 35  MV/m after buffered chemical polishing (BCP and up to 42  MV/m after electropolishing (EP. More recent work concentrated on fabrication and testing of multicell and nine-cell cavities. Several seamless two- and three-cell units were explored. Accelerating gradients E_{acc} of 30–35  MV/m were measured after BCP and E_{acc} up to 40  MV/m were reached after EP. Nine-cell niobium cavities combining three three-cell units were completed at the company E. Zanon. These cavities reached accelerating gradients of E_{acc}=30–35  MV/m. One cavity is successfully integrated in an XFEL cryomodule and is used in the operation of the FLASH linear accelerator at DESY. Additionally the fabrication of bimetallic single-cell and multicell NbCu cavities by hydroforming was successfully developed. Several NbCu clad single-cell and

  15. Numerical analysis of the effects of a high gradient magnetic field on flowing erythrocytes in a membrane oxygenator

    International Nuclear Information System (INIS)

    Mitamura, Yoshinori; Okamoto, Eiji

    2015-01-01

    This study was carried out to clarify the effect of a high gradient magnetic field on pressure characteristics of blood in a hollow fiber membrane oxygenator in a solenoid coil by means of numerical analysis. Deoxygenated erythrocytes are paramagnetic, and oxygenated erythrocytes are diamagnetic. Blood changes its magnetic susceptibility depending on whether it is carrying oxygen or not. Motion of blood was analyzed by solving the continuous equation and the Navier–Stokes equation. It was confirmed that oxygenation of deoxygenated blood in the downstream side of the applied magnetic field was effective for pressure rise in a non-uniform magnetic field. The pressure rise was enhanced greatly by an increase in magnetic field intensity. The results suggest that a membrane oxygenator works as an actuator and there is a possibility of self-circulation of blood through an oxygenator in a non-uniform magnetic field. - Highlights: • Effects of a gradient magnetic field on erythrocytes in an oxygenator were analyzed. • Blood changes magnetic susceptibility depending on if it is carrying oxygen or not. • Oxygenation of deoxygenated blood is effective for pressure rise in a magnetic field. • A membrane oxygenator works as an actuator. • There is a possibility of self-circulation of blood through an oxygenator

  16. Test of the beam effect on vacuum arc occurrence in a high-gradient accelerating structure for the CLIC project

    CERN Document Server

    AUTHOR|(CDS)2130409; Gagliardi, Martino

    A new generation of lepton colliders capable of reaching TeV energies is pres- ently under development, and to succeed in this task it is necessary to show that the technology for such a machine is available. The Compact Linear Collider (CLIC) is a possible design option among the future lepton collider projects. It consists of two normal-conducting linacs. Accelerating structures with a gradient of the order of 100 MV/m are necessary to reach the required high energies within a reasonable machine length. One of the strictest require- ments for such accelerating structures is a relatively low occurrence of vacuum arcs. CLIC prototype structures have been tested in the past, but only in absence of beam. In order to proof the feasibility of the high gradient technology for building a functional collider, it is necessary to understand the effect of the beam presence on the vacuum breakdowns. Tests of this type have never been performed previously. The main goal of this work is to provide a first measurement of t...

  17. Numerical analysis of the effects of a high gradient magnetic field on flowing erythrocytes in a membrane oxygenator

    Energy Technology Data Exchange (ETDEWEB)

    Mitamura, Yoshinori, E-mail: ymitamura@par.odn.ne.jp; Okamoto, Eiji, E-mail: okamoto@tspirit.tokai-u.jp

    2015-04-15

    This study was carried out to clarify the effect of a high gradient magnetic field on pressure characteristics of blood in a hollow fiber membrane oxygenator in a solenoid coil by means of numerical analysis. Deoxygenated erythrocytes are paramagnetic, and oxygenated erythrocytes are diamagnetic. Blood changes its magnetic susceptibility depending on whether it is carrying oxygen or not. Motion of blood was analyzed by solving the continuous equation and the Navier–Stokes equation. It was confirmed that oxygenation of deoxygenated blood in the downstream side of the applied magnetic field was effective for pressure rise in a non-uniform magnetic field. The pressure rise was enhanced greatly by an increase in magnetic field intensity. The results suggest that a membrane oxygenator works as an actuator and there is a possibility of self-circulation of blood through an oxygenator in a non-uniform magnetic field. - Highlights: • Effects of a gradient magnetic field on erythrocytes in an oxygenator were analyzed. • Blood changes magnetic susceptibility depending on if it is carrying oxygen or not. • Oxygenation of deoxygenated blood is effective for pressure rise in a magnetic field. • A membrane oxygenator works as an actuator. • There is a possibility of self-circulation of blood through an oxygenator.

  18. A permanently magnetized high gradient magnetic filter for glove-box cleaning and increasing HEPA filter life

    International Nuclear Information System (INIS)

    Watson, J.H.P.; Boorman, C.H.

    1991-01-01

    The purpose of this paper is to describe the structure and testing of a permanently magnetized magnetic filter on simulants for radioactive material. The experimental work was carried out at British Nuclear Fuels plc, Sellafield, England and in CEN/SCK, Mol, Belgium using Cr powder which is a good magnetic simulant for PuO 2 . The basis of the use of such a filter in the nuclear industry relies on the fact that much of the radioactive material is paramagnetic. In the last twenty years a separation technique has been developed which allows weakly paramagnetic particles of colloidal size to be separated from fluid which passes through the separator. This method is called high gradient magnetic separation (HGMS) and is accomplished by magnetizing a fine ferromagnetic wire matrix by an externally applied magnetic field. This paper describes a new approach to this problem, by using a magnetically hysteretic material to construct the ferromagnetic matrix, it has been possible to provide a magnetic field in the region of the matrix and also have a residual magnetization within the matrix. This provides extremely compact magnetic separation systems. There are some subtle differences between this separation system and conventional HGMS which makes the radial feed system, with all its advantages, almost mandatory for hysteretic HGMS

  19. SPS accelerating cavity

    CERN Multimedia

    CERN PhotoLab

    1976-01-01

    The SPS started up with 2 accelerating cavities (each consisting of 5 tank sections) in LSS3. They have a 200 MHz travelling wave structure (see 7411032 and 7802190) and 750 kW of power is fed to each of the cavities from a 1 MW tetrode power amplifier, located in a surface building above, via a coaxial transmission line. Clemens Zettler, builder of the SPS RF system, is standing at the side of one of the cavities. In 1978 and 1979 another 2 cavities were added and entered service in 1980. These were part of the intensity improvement programme and served well for the new role of the SPS as proton-antiproton collider. See also 7411032, 8011289, 8104138, 8302397.

  20. Dental Sealants Prevent Cavities

    Science.gov (United States)

    ... Digital Press Kit Read the MMWR Science Clips Dental Sealants Prevent Cavities Effective protection for children Language: ... more use of sealants and reimbursement of services. Dental care providers can Apply sealants to children at ...

  1. Statistical electromagnetics: Complex cavities

    NARCIS (Netherlands)

    Naus, H.W.L.

    2008-01-01

    A selection of the literature on the statistical description of electromagnetic fields and complex cavities is concisely reviewed. Some essential concepts, for example, the application of the central limit theorem and the maximum entropy principle, are scrutinized. Implicit assumptions, biased

  2. accelerating cavity from LEP

    CERN Multimedia

    This is an accelerating cavity from LEP, with a layer of niobium on the inside. Operating at 4.2 degrees above absolute zero, the niobium is superconducting and carries an accelerating field of 6 million volts per metre with negligible losses. Each cavity has a surface of 6 m2. The niobium layer is only 1.2 microns thick, ten times thinner than a hair. Such a large area had never been coated to such a high accuracy. A speck of dust could ruin the performance of the whole cavity so the work had to be done in an extremely clean environment. These challenging requirements pushed European industry to new achievements. 256 of these cavities are now used in LEP to double the energy of the particle beams.

  3. Hybrid vertical cavity laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2010-01-01

    A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide.......A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide....

  4. The Superconducting TESLA Cavities

    CERN Document Server

    Aune, B.; Bloess, D.; Bonin, B.; Bosotti, A.; Champion, M.; Crawford, C.; Deppe, G.; Dwersteg, B.; Edwards, D.A.; Edwards, H.T.; Ferrario, M.; Fouaidy, M.; Gall, P-D.; Gamp, A.; Gössel, A.; Graber, J.; Hubert, D.; Hüning, M.; Juillard, M.; Junquera, T.; Kaiser, H.; Kreps, G.; Kuchnir, M.; Lange, R.; Leenen, M.; Liepe, M.; Lilje, L.; Matheisen, A.; Möller, W-D.; Mosnier, A.; Padamsee, H.; Pagani, C.; Pekeler, M.; Peters, H-B.; Peters, O.; Proch, D.; Rehlich, K.; Reschke, D.; Safa, H.; Schilcher, T.; Schmüser, P.; Sekutowicz, J.; Simrock, S.; Singer, W.; Tigner, M.; Trines, D.; Twarowski, K.; Weichert, G.; Weisend, J.; Wojtkiewicz, J.; Wolff, S.; Zapfe, K.

    2000-01-01

    The conceptional design of the proposed linear electron-positron colliderTESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with anaccelerating gradient of Eacc >= 25 MV/m at a quality factor Q0 > 5E+9. Thedesign goal for the cavities of the TESLA Test Facility (TTF) linac was set tothe more moderate value of Eacc >= 15 MV/m. In a first series of 27industrially produced TTF cavities the average gradient at Q0 = 5E+9 wasmeasured to be 20.1 +- 6.2 MV/m, excluding a few cavities suffering fromserious fabrication or material defects. In the second production of 24 TTFcavities additional quality control measures were introduced, in particular aneddy-current scan to eliminate niobium sheets with foreign material inclusionsand stringent prescriptions for carrying out the electron-beam welds. Theaverage gradient of these cavities at Q0 = 5E+9 amounts to 25.0 +- 3.2 MV/mwith the exception of one cavity suffering from a weld defect. Hence only amoderate improvement in production and preparation technique...

  5. Effect of low-temperature baking on the radio-frequency properties of niobium superconducting cavities for particle accelerators

    International Nuclear Information System (INIS)

    Ciovati, Gianluigi

    2004-01-01

    Radio-frequency superconducting (SRF) cavities are widely used to accelerate a charged particle beam in particle accelerators. The performance of SRF cavities made of bulk niobium has significantly improved over the last ten years and is approaching the theoretical limit for niobium. Nevertheless, RF tests of niobium cavities are still showing some 'anomalous' losses that require a better understanding in order to reliably obtain better performance. These losses are characterized by a marked dependence of the surface resistance on the surface electromagnetic field and can be detected by measuring the quality factor of the resonator as a function of the peak surface field. A low-temperature (100-150 deg. C) 'in situ' bake under ultrahigh vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor at low field and a recovery from 'anomalous' losses (so-called 'Q drop') without field emission at higher field. A series of experiments with a CEBAF single-cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37-280 K and resonant frequency shift between 6-9.3 K provide information about the surface resistance, energy gap, penetration depth, and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity. The hydrogen content of small niobium samples inserted in the cavity during its surface preparation was analyzed with nuclear reaction analysis. The single-cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models. This paper

  6. Effect of low-temperature baking on the radio-frequency properties of niobium superconducting cavities for particle accelerators

    Science.gov (United States)

    Ciovati, Gianluigi

    2004-08-01

    Radio-frequency superconducting (SRF) cavities are widely used to accelerate a charged particle beam in particle accelerators. The performance of SRF cavities made of bulk niobium has significantly improved over the last ten years and is approaching the theoretical limit for niobium. Nevertheless, RF tests of niobium cavities are still showing some "anomalous" losses that require a better understanding in order to reliably obtain better performance. These losses are characterized by a marked dependence of the surface resistance on the surface electromagnetic field and can be detected by measuring the quality factor of the resonator as a function of the peak surface field. A low-temperature (100-150°C) "in situ" bake under ultrahigh vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor at low field and a recovery from "anomalous" losses (so-called "Q drop") without field emission at higher field. A series of experiments with a CEBAF single-cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37-280K and resonant frequency shift between 6-9.3K provide information about the surface resistance, energy gap, penetration depth, and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity. The hydrogen content of small niobium samples inserted in the cavity during its surface preparation was analyzed with nuclear reaction analysis. The single-cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models. This paper describes

  7. The effects of Eu-concentrations on the luminescent properties of SrF2:Eu nanophosphor

    International Nuclear Information System (INIS)

    Yagoub, M.Y.A.; Swart, H.C.; Noto, L.L.; O’Connel, J.H.; Lee, M.E.; Coetsee, E.

    2014-01-01

    SrF 2 :Eu nanophosphors were successfully synthesized by the hydrothermal method. The structure of the nanophosphors was investigated with x-ray diffraction. The average crystallite size calculated using the Scherrer equation was in the range of 7.0 nm. The photoluminescence of Eu doped as-prepared SrF 2 nanophosphors were studied using different excitation sources. The samples showed emission from both the Eu oxidation states, Eu 2+ and Eu 3+ . At low Eu concentrations the emission from Eu 2+ centered at 416 nm was more dominant. While the narrow band of Eu 3+ emission intensity increased with an increase in the Eu concentration. High resolution x-ray photoelectron spectroscopy results indicated that the Eu was indeed in both Eu 2+ and Eu 3+ valance states. The presence of Eu 2+ and Eu 3+ in the system largely enhanced the response of the Eu 3+ under ultraviolet excitation. The time of flight-secondary ion mass spectrometry results suggested that the energy transfer between two ions was likely to occur. The relative photoluminescence intensity of the Eu 2+ rapidly decreased with an increasing laser beam irradiating time. This result would make the current Eu 2+ doped SrF 2 samples unsuitable candidates for several applications, such as white light-emitting diodes and wavelength conversion films for silicon photovoltaic cells. - Highlights: • SrF 2 : Eu nanophosphors were successfully synthesised (hydrothermal technique). • PL and XPS results showed enhanced absorption response of Eu 3+ UV excitation. • Eu concentrations more than 5 mol% improved fluorescence emission. • TOF-SIMS results suggested that the energy transfer from Eu 2+ to Eu 3+ is dominant

  8. Theoretical and experimental study of a modular accelerating structure of travelling waves sections for high gradient tests (MECCANO); Etude theorique et experimentale d`une structure acceleratrice a ondes progressives demontable pour des tests fort gradient (Structure dite ``MECCANO``)

    Energy Technology Data Exchange (ETDEWEB)

    Chanudet, M

    1996-06-04

    A modular system, MECCANO, has been developed at the Laboratoire de l`Accelerateur Lineaire d`Orsay to study the physical and technical phenomena of high electric fields in travelling waves structures in the context of future linear colliders which can reach TeV energies. The behaviour of the electric field inside the section MECCANO is considered from the theoretical point of view with numerical simulations and analytical representations and from the experimental side with low and high power measurements. An infinite and uniform structure is classically described by series of RLC resonant circuits. The basic RF properties of the fundamental mode are given. For a finite section, the matching of a forward or backward travelling wave of any phase advance per cell is also represented by means of RLC circuits. The variations of the reflection and transmission properties of the structure with frequency and a new procedure to match couplers have been modelled and experimentally verified. The electromagnetic behaviour of each cavity and of the whole structure have been studied, the fundamental and first high order modes have been simulated by 2D or 3D codes and measured at low power. The matching of the phase, the amplitude and the reflection level of the accelerator is described. This procedure is found to be extremely delicate due to the abrupt changes in the geometry of the cavities. The structure has been tested at fields superior to 150 MV/m. The behaviour of some materials and surface layers subject to high gradients are presented. (author) 46 refs.

  9. Quantum efficiency temporal response and lifetime of a GaAs cathode in SRF electron gun

    Energy Technology Data Exchange (ETDEWEB)

    Wang, E.; Ben-Zvi, I.; Kewisch, J.; Burrill, A.; Rao, T.; Wu, Q.; Holmes, D.

    2010-05-23

    RF electron guns with a strained super lattice GaAs cathode can generate polarized electron beam of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode's surface. In a normal conducting RF gun, the extremely high vaccum required by these cathodes can not be met. We report on an experiment with a superconducting SRF gun, which can maintain a vacuum of nearly 10-12 torr because of cryo-pumping at the temperature of 4.2K. With conventional activation, we obtained a QE of 3% at 532 nm, with lifetime of nearly 3 days in the preparation chamber. We plan to use this cathode in a 1.3 GHz 1/2 cell SRF gun to study its performance. In addition, we studied the multipacting at the location of cathode. A new model based on the Forkker-Planck equation which can estimate the bunch length of the electron beam is discussed in this paper. Future particle accelerators such as eRHIC and ILC require high brightness, high current polarized electrons Recently, using a superlattice crystal, the maximum polarization of 95% was reached. Activation with Cs,O lowers the electron affinity and makes it energetically possible for all the electrons excited in to the conduction band and reach the surface to escape into the vacuum. Presently the polarized electron sources are based on DC gun, such as that at the CEBAF at Jlab. In these devices, the life time of the cathode is extended due to the reduced back bombardment in their UHV conditions. However, the low accelerating gradient of the DC guns lead to poor longitudinal emittance. The higher accelerating gradient of the RF gun generates low emittance beams. Superconducting RF guns combine the excellent vacuum conditions of the DC guns with the higher accelerating gradients of the RF guns and provide potentially a long lived cathode with very low transverse and longitudinal emittance. In our work at BNL, we successfully activated the GaAs. The quantum efficient is 3% at 532 nm and is

  10. Quantum efficiency temporal response and lifetime of a GaAs cathode in SRF electron gun

    International Nuclear Information System (INIS)

    Wang, E.; Ben-Zvi, I.; Kewisch, J.; Burrill, A.; Rao, T.; Wu, Q.; Holmes, D.

    2010-01-01

    RF electron guns with a strained super lattice GaAs cathode can generate polarized electron beam of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode's surface. In a normal conducting RF gun, the extremely high vaccum required by these cathodes can not be met. We report on an experiment with a superconducting SRF gun, which can maintain a vacuum of nearly 10-12 torr because of cryo-pumping at the temperature of 4.2K. With conventional activation, we obtained a QE of 3% at 532 nm, with lifetime of nearly 3 days in the preparation chamber. We plan to use this cathode in a 1.3 GHz 1/2 cell SRF gun to study its performance. In addition, we studied the multipacting at the location of cathode. A new model based on the Forkker-Planck equation which can estimate the bunch length of the electron beam is discussed in this paper. Future particle accelerators such as eRHIC and ILC require high brightness, high current polarized electrons Recently, using a superlattice crystal, the maximum polarization of 95% was reached. Activation with Cs,O lowers the electron affinity and makes it energetically possible for all the electrons excited in to the conduction band and reach the surface to escape into the vacuum. Presently the polarized electron sources are based on DC gun, such as that at the CEBAF at Jlab. In these devices, the life time of the cathode is extended due to the reduced back bombardment in their UHV conditions. However, the low accelerating gradient of the DC guns lead to poor longitudinal emittance. The higher accelerating gradient of the RF gun generates low emittance beams. Superconducting RF guns combine the excellent vacuum conditions of the DC guns with the higher accelerating gradients of the RF guns and provide potentially a long lived cathode with very low transverse and longitudinal emittance. In our work at BNL, we successfully activated the GaAs. The quantum efficient is 3% at 532 nm and is expected

  11. Maximum Potential Hydrogen Gas Retention in the sRF Resin Ion Exchange Column for the LAWPS Process

    Energy Technology Data Exchange (ETDEWEB)

    Gauglitz, Phillip A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wells, Beric E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bottenus, Courtney LH [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Schonewill, Philip P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2018-01-22

    The Low-Activity Waste Pretreatment System (LAWPS) is being developed to provide treated supernatant liquid from the Hanford tank farms directly to the Low-Activity Waste (LAW) Vitrification Facility at the Hanford Tank Waste Treatment and Immobilization Plant. The design and development of the LAWPS is being conducted by Washington River Protection Solutions, LLC. A key process in LAWPS is the removal of radioactive Cs in ion exchange (IX) columns filled with spherical resorcinol-formaldehyde (sRF) resin. One accident scenario being evaluated is the loss of liquid flow through the sRF resin bed after it has been loaded with radioactive Cs and hydrogen gas is being generated by radiolysis. In normal operations, the generated hydrogen is expected to remain dissolved in the liquid and be continuously removed by liquid flow. For an accident scenario with a loss of flow, hydrogen gas can be retained within the IX column both in the sRF resin and below the bottom screen that supports the resin within the column. The purpose of this report is to summarize calculations that estimate the upper-bound volume of hydrogen gas that can be retained in the column and potentially be released to the headspace of the IX column or to process equipment connected to the IX column and, thus, pose a flammability hazard.

  12. Differential Accumulation of Mercury and Selenium in Brown Trout Tissues of a High-Gradient Urbanized Stream in Colorado, USA.

    Science.gov (United States)

    Herrmann, S J; Nimmo, D R; Carsella, J S; Herrmann-Hoesing, L M; Turner, J A; Gregorich, J M; Heuvel, B D Vanden; Nehring, R B; Foutz, H P

    2016-02-01

    Total mercury (THg) and selenium (Se) were analyzed by Inductively Coupled Plasma Mass Spectrometry in 11 internal and external tissues and stomach contents from 23 brown trout, Salmo trutta, of a 22.9-km reach of a high-gradient stream (upper Fountain Creek) in Colorado, USA, impacted by coal-fired power plants, shale deposits, and urbanization. Trout and water were sampled from four sites ranging from 2335 to 1818 m elevation. Lengths, weights, and ages of fish between pairs of the four sites were not significantly different. The dry weight (dw) to wet weight (ww) conversion factor for each tissue was calculated with egg-ovary highest at 0.379 and epaxial muscle fourth highest at 0.223. THg and Se in stomach contents indicated diet and not ambient water was the major source of Hg and Se bioaccumulated. Mean THg ww in kidney was 40.33 µg/kg, and epaxial muscle second highest at 36.76 µg/kg. None of the tissues exceeded the human critical threshold for Hg. However, all 23 trout had at least one tissue type that exceeded 0.02 mg/kg THg ww for birds, and four trout tissues exceeded 0.1 mg/kg THg ww for mammals, indicating that piscivorous mammals and birds should be monitored. Se concentrations in tissues varied depending on ww or dw listing. Mean Se dw in liver was higher than ovary at the uppermost site and the two lower sites. Liver tissue, in addition to egg-ovary, should be utilized as an indicator tissue for Se toxicity.

  13. Investigation of niobium surface structure and composition for improvement of superconducting radio-frequency cavities

    Science.gov (United States)

    Trenikhina, Yulia

    Nano-scale investigation of intrinsic properties of niobium near-surface is a key to control performance of niobium superconducting radio-frequency cavities. Mechanisms responsible for the performance limitations and their empirical remedies needs to be justified in order to reproducibly control fabrication of SRF cavities with desired characteristics. The high field Q-slope and mechanism behind its cure (120°C mild bake) were investigated by comparison of the samples cut out of the cavities with high and low dissipation regions. Material evolution during mild field Q-slope nitrogen treatment was characterized using the coupon samples as well as samples cut out of nitrogen treated cavity. Evaluation of niobium near-surface state after some typical and novel cavity treatments was accomplished. Various TEM techniques, SEM, XPS, AES, XRD were used for the structural and chemical characterization of niobium near-surface. Combination of thermometry and structural temperature-dependent comparison of the cavity cutouts with different dissipation characteristics revealed precipitation of niobium hydrides to be the reason for medium and high field Q-slopes. Step-by-step effect of the nitrogen treatment processing on niobium surface was studied by analytical and structural characterization of the cavity cutout and niobium samples, which were subject to the treatment. Low concentration nitrogen doping is proposed to explain the benefit of nitrogen treatment. Chemical characterization of niobium samples before and after various surface processing (Electropolishing (EP), 800°C bake, hydrofluoric acid (HF) rinsing) showed the differences that can help to reveal the microscopic effects behind these treatments as well as possible sources of surface contamination.

  14. Single atoms on demand for cavity QED experiments

    International Nuclear Information System (INIS)

    Dotsenko, I.

    2007-01-01

    Cavity quantum electrodynamics (cavity QED) describes electromagnetic fields in a confined space and the radiative properties of atoms in such fields. The simplest example of such system is a single atom interacting with one mode of a high-finesse resonator. Besides observation and exploration of fundamental quantum mechanical effects, this system bears a high potential for applications quantum information science such as, e.g., quantum logic gates, quantum communication and quantum teleportation. In this thesis I present an experiment on the deterministic coupling of a single neutral atom to the mode of a high-finesse optical resonator. In Chapter 1 I describe our basic techniques for trapping and observing single cesium atoms. As a source of single atoms we use a high-gradient magneto-optical trap, which captures the atoms from background gas in a vacuum chamber and cools them down to millikelvin temperatures. The atoms are then transferred without loss into a standing-wave dipole trap, which provides a conservative potential required for experiments on atomic coherence such as quantum information processing and metrology on trapped atoms. Moreover, shifting the standing-wave pattern allows us to deterministically transport the atoms (Chapter 2). In combination with nondestructive fluorescence imaging of individual trapped atoms, this enables us to control their position with submicrometer precision over several millimeters along the dipole trap. The cavity QED system can distinctly display quantum behaviour in the so-called strong coupling regime, i.e., when the coherent atom-cavity coupling rate dominates dissipation in the system. This sets the main requirements on the resonator's properties: small mode volume and high finesse. Chapter 3 is devoted to the manufacturing, assembling, and testing of an ultra-high finesse optical Fabry-Perot resonator, stabilized to the atomic transition. In Chapter 4 I present the transportation of single atoms into the cavity

  15. Single atoms on demand for cavity QED experiments

    Energy Technology Data Exchange (ETDEWEB)

    Dotsenko, I.

    2007-09-06

    Cavity quantum electrodynamics (cavity QED) describes electromagnetic fields in a confined space and the radiative properties of atoms in such fields. The simplest example of such system is a single atom interacting with one mode of a high-finesse resonator. Besides observation and exploration of fundamental quantum mechanical effects, this system bears a high potential for applications quantum information science such as, e.g., quantum logic gates, quantum communication and quantum teleportation. In this thesis I present an experiment on the deterministic coupling of a single neutral atom to the mode of a high-finesse optical resonator. In Chapter 1 I describe our basic techniques for trapping and observing single cesium atoms. As a source of single atoms we use a high-gradient magneto-optical trap, which captures the atoms from background gas in a vacuum chamber and cools them down to millikelvin temperatures. The atoms are then transferred without loss into a standing-wave dipole trap, which provides a conservative potential required for experiments on atomic coherence such as quantum information processing and metrology on trapped atoms. Moreover, shifting the standing-wave pattern allows us to deterministically transport the atoms (Chapter 2). In combination with nondestructive fluorescence imaging of individual trapped atoms, this enables us to control their position with submicrometer precision over several millimeters along the dipole trap. The cavity QED system can distinctly display quantum behaviour in the so-called strong coupling regime, i.e., when the coherent atom-cavity coupling rate dominates dissipation in the system. This sets the main requirements on the resonator's properties: small mode volume and high finesse. Chapter 3 is devoted to the manufacturing, assembling, and testing of an ultra-high finesse optical Fabry-Perot resonator, stabilized to the atomic transition. In Chapter 4 I present the transportation of single atoms into the

  16. Heat load of a P-doped GaAs photocathode in SRF electron gun

    International Nuclear Information System (INIS)

    Wang, E.; Ben-Zvi, I.; Kewisch, J.; Burrill, A.; Rao, T.; Wu, Q.; Jain, A.; Gupta, R.; Holmes, D.

    2010-01-01

    Many efforts were made over the last decades to develop a better polarized electron source for the high energy physics. Several laboratories operate DC guns with the Gallium-Arsenide photo-cathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved using a Superconducting RF electron gun, which delivers beams of higher brightness than DC guns does, because the field gradient at the cathode is higher. SRF guns with metal cathodes and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since the cathode will be normal conducting, the problem about the heat load stemming from the cathode arises. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and the verification by measuring the quality factor of the gun with and without cathode.

  17. Longitudinal conductivity of LaF3/SrF2 multilayer heterostructures.

    Science.gov (United States)

    Vergentev, Tikhon; Banshchikov, Alexander; Filimonov, Alexey; Koroleva, Ekaterina; Sokolov, Nikolay; Wurz, Marc Christopher

    2016-01-01

    LaF 3 /SrF 2 multilayer heterostructures with thicknesses of individual layers in the range 5-100 nm have been grown on MgO(100) substrates using molecular beam epitaxy. The longitudinal conductivity of the films has been measured using impedance spectroscopy in the frequency range 10 -1 -10 6  Hz and a temperature range 300-570 K. The ionic DC conductivities have been determined from Nyquist impedance diagrams and activation energies from the Arrhenius-Frenkel equation. An increase of the DC conductivity has been observed to accompany decreased layer thickness for various thicknesses as small as 25 nm. The greatest conductivity has been shown for a multilayer heterostructure having thicknesses of 25 nm per layer. The structure has a conductivity two orders of magnitude greater than pure LaF 3 bulk material. The increasing conductivity can be understood as a redistribution of charge carriers through the interface due to differing chemical potentials of the materials, by strong lattice-constant mismatch, and/or by formation of a solid La 1-x Sr x F 3-x solution at the interface during the growth process.

  18. Cryogenic infrastructure for Fermilab's ILC vertical cavity test facility

    Energy Technology Data Exchange (ETDEWEB)

    Carcagno, R.; Ginsburg, C.; Huang, Y.; Norris, B.; Ozelis, J.; Peterson, T.; Poloubotko, V.; Rabehl, R.; Sylvester, C.; Wong, M.; /Fermilab

    2006-06-01

    Fermilab is building a Vertical Cavity Test Facility (VCTF) to provide for R&D and pre-production testing of bare 9-cell, 1.3-GHz superconducting RF (SRF) cavities for the International Linear Collider (ILC) program. This facility is located in the existing Industrial Building 1 (IB1) where the Magnet Test Facility (MTF) also resides. Helium and nitrogen cryogenics are shared between the VCTF and MTF including the existing 1500-W at 4.5-K helium refrigerator with vacuum pumping for super-fluid operation (125-W capacity at 2-K). The VCTF is being constructed in multiple phases. The first phase is scheduled for completion in mid 2007, and includes modifications to the IB1 cryogenic infrastructure to allow helium cooling to be directed to either the VCTF or MTF as scheduling demands require. At this stage, the VCTF consists of one Vertical Test Stand (VTS) cryostat for the testing of one cavity in a 2-K helium bath. Planning is underway to provide a total of three Vertical Test Stands at VCTF, each capable of accommodating two cavities. Cryogenic infrastructure improvements necessary to support these additional VCTF test stands include a dedicated ambient temperature vacuum pump, a new helium purification skid, and the addition of helium gas storage. This paper describes the system design and initial cryogenic operation results for the first VCTF phase, and outlines future cryogenic infrastructure upgrade plans for expanding to three Vertical Test Stands.

  19. Thermal study of a cryogen-less MgB{sub 2} cavity

    Energy Technology Data Exchange (ETDEWEB)

    Holzbauer, J.P., E-mail: jeremiah@fnal.gov; Nassiri, A.

    2014-12-11

    Recent efforts towards production of high-quality magnesium diboride (MgB{sub 2}) coatings have raised the possibility of producing usable accelerating cavities. Work continues to reliably produce films of sufficient quality over the large, complex surface area of an accelerating cavity, but this technology would open many interesting technical opportunities. One of these is to replace the traditionally required liquid helium cryogenic systems with a dry system based on cryocoolers. This is made possible by the much higher T{sub c} of MgB{sub 2}, allowing operation closer to 30 K where cryocooler efficiency becomes competitive with alternative systems. This removes the need for pressure vessels in the cryomodule as well as internal distribution systems, greatly simplifying cryomodule design and fabrication. The lack of uniform cooling over the cavity surface, however, complicates behavior by coupling RF losses, heat leak, and cooling design in a way not seen in traditional SRF cavities. In this paper, these complexities are explored, including realistic cryocooler performance, temperature dependant RF losses, and standard thermal management challenges.

  20. Prediction of the Lorentz Force Detuning and Pressure Sensitivity for a Pillbox Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Parise, M. [Fermilab

    2018-04-23

    The Lorentz Force Detuning (LFD) and the pressure sensitivity are two critical concerns during the design of a Superconducting Radio Frequency (SRF) cavity resonator. The mechanical deformation of the bare Niobium cavity walls, due to the electromagnetic fields and fluctuation of the external pressure in the Helium bath, can dynamically and statically detune the frequency of the cavity and can cause beam phase errors. The frequency shift can be compensated by additional RF power, that is required to maintain the accelerating gradient, or by sophisticated tuning mechanisms and control-compensation algorithms. Passive stiffening is one of the simplest and most effective tools that can be used during the early design phase, capable of satisfying the Radio Frequency (RF) requisites. This approach requires several multiphysics simulations as well as a deep mechanical and RF knowledge of the phenomena involved. In this paper, is presented a new numerical model for a pillbox cavity that can predict the frequency shifts caused by the LFD and external pressure. This method allows to greatly reduce the computational effort, which is necessary to meet the RF requirements and to keep track of the frequency shifts without using the time consuming multiphysics simulations.

  1. Roughness analysis applied to niobium thin films grown on MgO(001) surfaces for superconducting radio frequency cavity applications

    Science.gov (United States)

    Beringer, D. B.; Roach, W. M.; Clavero, C.; Reece, C. E.; Lukaszew, R. A.

    2013-02-01

    This paper describes surface studies to address roughness issues inherent to thin film coatings deposited onto superconducting radio frequency (SRF) cavities. This is particularly relevant for multilayered thin film coatings that are being considered as a possible scheme to overcome technical issues and to surpass the fundamental limit of ˜50MV/m accelerating gradient achievable with bulk niobium. In 2006, a model by Gurevich [Appl. Phys. Lett. 88, 012511 (2006)APPLAB0003-695110.1063/1.2162264] was proposed to overcome this limit that involves coating superconducting layers separated by insulating ones onto the inner walls of the cavities. Thus, we have undertaken a systematic effort to understand the dynamic evolution of the Nb surface under specific deposition thin film conditions onto an insulating surface in order to explore the feasibility of the proposed model. We examine and compare the morphology from two distinct Nb/MgO series, each with its own epitaxial registry, at very low growth rates and closely examine the dynamical scaling of the surface features during growth. Further, we apply analysis techniques such as power spectral density to the specific problem of thin film growth and roughness evolution to qualify the set of deposition conditions that lead to successful SRF coatings.

  2. Roughness analysis applied to niobium thin films grown on MgO(001 surfaces for superconducting radio frequency cavity applications

    Directory of Open Access Journals (Sweden)

    D. B. Beringer

    2013-02-01

    Full Text Available This paper describes surface studies to address roughness issues inherent to thin film coatings deposited onto superconducting radio frequency (SRF cavities. This is particularly relevant for multilayered thin film coatings that are being considered as a possible scheme to overcome technical issues and to surpass the fundamental limit of ∼50  MV/m accelerating gradient achievable with bulk niobium. In 2006, a model by Gurevich [Appl. Phys. Lett. 88, 012511 (2006APPLAB0003-695110.1063/1.2162264] was proposed to overcome this limit that involves coating superconducting layers separated by insulating ones onto the inner walls of the cavities. Thus, we have undertaken a systematic effort to understand the dynamic evolution of the Nb surface under specific deposition thin film conditions onto an insulating surface in order to explore the feasibility of the proposed model. We examine and compare the morphology from two distinct Nb/MgO series, each with its own epitaxial registry, at very low growth rates and closely examine the dynamical scaling of the surface features during growth. Further, we apply analysis techniques such as power spectral density to the specific problem of thin film growth and roughness evolution to qualify the set of deposition conditions that lead to successful SRF coatings.

  3. Roughness analysis applied to niobium thin films grown on MgO(001) surfaces for superconducting radio frequency cavity applications

    Energy Technology Data Exchange (ETDEWEB)

    Beringer, D. B. [College of William and Mary, Williamsburg, VA (United States). Dept. of Physics; Roach, W. M. [College of William and Mary, Williamsburg, VA (United States). Dept. of Applied Science; Clavero, C. [College of William and Mary, Williamsburg, VA (United States). Dept. of Applied Science; Reece, C. E. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Lukaszew, R. A. [College of William and Mary, Williamsburg, VA (United States). Dept. of Physics; College of William and Mary, Williamsburg, VA (United States). Dept. of Applied Science

    2013-02-05

    This paper describes surface studies to address roughness issues inherent to thin film coatings deposited onto superconducting radio frequency (SRF) cavities. This is particularly relevant for multilayered thin film coatings that are being considered as a possible scheme to overcome technical issues and to surpass the fundamental limit of ~500 MV/m accelerating gradient achievable with bulk niobium. In 2006, a model by Gurevich [ Appl. Phys. Lett. 88 012511 (2006)] was proposed to overcome this limit that involves coating superconducting layers separated by insulating ones onto the inner walls of the cavities. Thus, we have undertaken a systematic effort to understand the dynamic evolution of the Nb surface under specific deposition thin film conditions onto an insulating surface in order to explore the feasibility of the proposed model. We examine and compare the morphology from two distinct Nb/MgO series, each with its own epitaxial registry, at very low growth rates and closely examine the dynamical scaling of the surface features during growth. Further, we apply analysis techniques such as power spectral density to the specific problem of thin film growth and roughness evolution to qualify the set of deposition conditions that lead to successful SRF coatings.

  4. Development of a multi-scale simulation model of tube hydroforming for superconducting RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H.S. [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH (United States); Sumption, M.D., E-mail: sumption.3@osu.edu [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH (United States); Bong, H.J. [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH (United States); Lim, H. [Sandia National Laboratories, Albuquerque, NM (United States); Collings, E.W. [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH (United States)

    2017-01-02

    This work focuses on finite element modeling of the hydroforming process for niobium tubes intended for use in superconducting radio frequency (SRF) cavities. The hydroforming of tubular samples into SRF-relevant shapes involves the complex geometries and loading conditions which develop during the deformation, as well as anisotropic materials properties. Numerical description of the process entails relatively complex numerical simulations. A crystal plasticity (CP) model was constructed that included the evolution of crystallographic orientation during deformation as well as the anisotropy of tubes in all directions and loading conditions. In this work we demonstrate a multi-scale simulation approach which uses both microscopic CP and macroscopic continuum models. In this approach a CP model (developed and implemented into ABAQUS using UMAT) was used for determining the flow stress curve only under bi-axial loading in order to reduce the computing time. The texture of the materials obtained using orientation imaging microscopy (OIM) and tensile test data were inputs for this model. Continuum FE analysis of tube hydroforming using the obtained constitutive equation from the CP modeling was then performed and compared to the results of hydraulic bulge testing. The results show that high quality predictions of the deformation under hydroforming of Nb tubes can be obtained using CP-FEM based on their known texture and the results of tensile tests. The importance of the CP-FEM based approach is that it reduces the need for hydraulic bulge testing, using a relatively simple computational approach.

  5. Development of a multi-scale simulation model of tube hydroforming for superconducting RF cavities

    International Nuclear Information System (INIS)

    Kim, H.S.; Sumption, M.D.; Bong, H.J.; Lim, H.; Collings, E.W.

    2017-01-01

    This work focuses on finite element modeling of the hydroforming process for niobium tubes intended for use in superconducting radio frequency (SRF) cavities. The hydroforming of tubular samples into SRF-relevant shapes involves the complex geometries and loading conditions which develop during the deformation, as well as anisotropic materials properties. Numerical description of the process entails relatively complex numerical simulations. A crystal plasticity (CP) model was constructed that included the evolution of crystallographic orientation during deformation as well as the anisotropy of tubes in all directions and loading conditions. In this work we demonstrate a multi-scale simulation approach which uses both microscopic CP and macroscopic continuum models. In this approach a CP model (developed and implemented into ABAQUS using UMAT) was used for determining the flow stress curve only under bi-axial loading in order to reduce the computing time. The texture of the materials obtained using orientation imaging microscopy (OIM) and tensile test data were inputs for this model. Continuum FE analysis of tube hydroforming using the obtained constitutive equation from the CP modeling was then performed and compared to the results of hydraulic bulge testing. The results show that high quality predictions of the deformation under hydroforming of Nb tubes can be obtained using CP-FEM based on their known texture and the results of tensile tests. The importance of the CP-FEM based approach is that it reduces the need for hydraulic bulge testing, using a relatively simple computational approach.

  6. Progress and Plans for R&D and the Conceptual Design of the ILC High Gradient Structures

    CERN Document Server

    Padamsee, Hasan

    2005-01-01

    Gradients and Q's in the dominant ILC candidate structure have shown steady improvement, reaching 35-40 MV/m in the last year by using the best techniques of electropolishing, high pressure rinsing and 120 C baking for 48 hours. Progress and plans for t his structure will be reviewed. Above 40 MV/m, the surface magnetic field encroaches the rf critical magnetic field, believed to fall between 1750 and 2000 Oe, depending on the theory. One way to circumvent the limit is to modify the cavity shape to reduc e the ratio of peak magnetic to accelerating field. Two candidate shapes are evolving, the Re-entrant shape and the Low-Loss shape. Although field emission is aggravated by higher electric fields, it does not present a brick wall limit because high pressu re rinsing at 100 bar eliminates microparticles which cause field emission. Fundamental and higher mode properties of these new shapes will be compared with the dominant ILC candidate. Results of single and multicell cavities will be presented. The record fi...

  7. Video Toroid Cavity Imager

    Energy Technology Data Exchange (ETDEWEB)

    Gerald, Rex E. II; Sanchez, Jairo; Rathke, Jerome W.

    2004-08-10

    A video toroid cavity imager for in situ measurement of electrochemical properties of an electrolytic material sample includes a cylindrical toroid cavity resonator containing the sample and employs NMR and video imaging for providing high-resolution spectral and visual information of molecular characteristics of the sample on a real-time basis. A large magnetic field is applied to the sample under controlled temperature and pressure conditions to simultaneously provide NMR spectroscopy and video imaging capabilities for investigating electrochemical transformations of materials or the evolution of long-range molecular aggregation during cooling of hydrocarbon melts. The video toroid cavity imager includes a miniature commercial video camera with an adjustable lens, a modified compression coin cell imager with a fiat circular principal detector element, and a sample mounted on a transparent circular glass disk, and provides NMR information as well as a video image of a sample, such as a polymer film, with micrometer resolution.

  8. Metasurface external cavity laser

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Luyao, E-mail: luyaoxu.ee@ucla.edu; Curwen, Christopher A.; Williams, Benjamin S. [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); California NanoSystems Institute, University of California, Los Angeles, California 90095 (United States); Hon, Philip W. C.; Itoh, Tatsuo [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Chen, Qi-Sheng [Northrop Grumman Aerospace Systems, Redondo Beach, California 90278 (United States)

    2015-11-30

    A vertical-external-cavity surface-emitting-laser is demonstrated in the terahertz range, which is based upon an amplifying metasurface reflector composed of a sub-wavelength array of antenna-coupled quantum-cascade sub-cavities. Lasing is possible when the metasurface reflector is placed into a low-loss external cavity such that the external cavity—not the sub-cavities—determines the beam properties. A near-Gaussian beam of 4.3° × 5.1° divergence is observed and an output power level >5 mW is achieved. The polarized response of the metasurface allows the use of a wire-grid polarizer as an output coupler that is continuously tunable.

  9. Earth-ionosphere cavity

    International Nuclear Information System (INIS)

    Tran, A.; Polk, C.

    1976-01-01

    To analyze ELF wave propagation in the earth-ionosphere cavity, a flat earth approximation may be derived from the exact equations, which are applicable to the spherical cavity, by introducing a second-order or Debye approximation for the spherical Hankel functions. In the frequency range 3 to 30 Hz, however, the assumed conditions for the Debye approximation are not satisfied. For this reason an exact evaluation of the spherical Hankel functions is used to study the effects of the flat earth approximation on various propagation and resonance parameters. By comparing the resonance equation for a spherical cavity with its flat earth counterpart and by assuming that the surface impedance Z/sub i/ at the upper cavity boundary is known, the relation between the eigenvalue ν and S/sub v/, the sine of the complex angle of incidence at the lower ionosphere boundary, is established as ν(ν + 1) = (kaS/sub v/) 2 . It is also shown that the approximation ν(ν + 1) approximately equals (ν + 1/2) 2 which was used by some authors is not adequate below 30 Hz. Numerical results for both spherical and planar stratification show that (1) planar stratification is adequate for the computation of the lowest three ELF resonance frequencies to within 0.1 Hz; (2) planar stratification will lead to errors in cavity Q and wave attenuation which increase with frequency; (3) computation of resonance frequencies to within 0.1 Hz requires the extension of the lower boundary of the ionosphere to a height where the ratio of conduction current to displacement current, (sigma/ωepsilon 0 ), is less than 0.3; (4) atmospheric conductivity should be considered down to ground level in computing cavity Q and wave attenuation

  10. Materials for superconducting cavities

    International Nuclear Information System (INIS)

    Bonin, B.

    1996-01-01

    The ideal material for superconducting cavities should exhibit a high critical temperature, a high critical field, and, above all, a low surface resistance. Unfortunately, these requirements can be conflicting and a compromise has to be found. To date, most superconducting cavities for accelerators are made of niobium. The reasons for this choice are discussed. Thin films of other materials such as NbN, Nb 3 Sn, or even YBCO compounds can also be envisaged and are presently investigated in various laboratories. It is shown that their success will depend critically on the crystalline perfection of these films. (author)

  11. Experimental investigation of cavity flows

    Energy Technology Data Exchange (ETDEWEB)

    Loeland, Tore

    1999-12-31

    This thesis uses LDV (Laser Doppler Velocimetry), PIV (Particle Image Velocimetry) and Laser Sheet flow Visualisation to study flow inside three different cavity configurations. For sloping cavities, the vortex structure inside the cavities is found to depend upon the flow direction past the cavity. The shape of the downstream corner is a key factor in destroying the boundary layer flow entering the cavity. The experimental results agree well with numerical simulations of the same geometrical configurations. The results of the investigations are used to find the influence of the cavity flow on the accuracy of the ultrasonic flowmeter. A method to compensate for the cavity velocities is suggested. It is found that the relative deviation caused by the cavity velocities depend linearly on the pipe flow. It appears that the flow inside the cavities should not be neglected as done in the draft for the ISO technical report on ultrasonic flowmeters. 58 refs., 147 figs., 2 tabs.

  12. Experimental investigation of cavity flows

    Energy Technology Data Exchange (ETDEWEB)

    Loeland, Tore

    1998-12-31

    This thesis uses LDV (Laser Doppler Velocimetry), PIV (Particle Image Velocimetry) and Laser Sheet flow Visualisation to study flow inside three different cavity configurations. For sloping cavities, the vortex structure inside the cavities is found to depend upon the flow direction past the cavity. The shape of the downstream corner is a key factor in destroying the boundary layer flow entering the cavity. The experimental results agree well with numerical simulations of the same geometrical configurations. The results of the investigations are used to find the influence of the cavity flow on the accuracy of the ultrasonic flowmeter. A method to compensate for the cavity velocities is suggested. It is found that the relative deviation caused by the cavity velocities depend linearly on the pipe flow. It appears that the flow inside the cavities should not be neglected as done in the draft for the ISO technical report on ultrasonic flowmeters. 58 refs., 147 figs., 2 tabs.

  13. Proof-of-principle demonstration of Nb{sub 3}Sn superconducting radiofrequency cavities for high Q{sub 0} applications

    Energy Technology Data Exchange (ETDEWEB)

    Posen, S., E-mail: sep93@cornell.edu; Liepe, M.; Hall, D. L. [Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York 14853 (United States)

    2015-02-23

    Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. This contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb{sub 3}Sn. In this paper, we present results for single cell cavities coated with Nb{sub 3}Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q{sub 0} out to medium fields was reproducible, resulting in an average quench field of 14 MV/m and an average 4.2 K Q{sub 0} at quench of 8 × 10{sup 9}. In each case, the peak surface magnetic field at quench was well above H{sub c1}, showing that it is not a limiting field in these cavities. The coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that—taking into account the thermodynamic efficiency of the cryogenic plant—the 4.2 K Q{sub 0} values obtained meet the AC power consumption requirements of state-of-the-art high duty factor accelerators, making this a proof-of-principle demonstration for Nb{sub 3}Sn cavities in future applications.

  14. Mechanical study of the Saclay piezo tuner PTS (piezo tuning system) Care-SRF-WP8

    International Nuclear Information System (INIS)

    Bosland, P.; Wu, B.

    2005-03-01

    The present tuner is working inside Tesla test facility's cryo-modules without any piezo actuator. Thus the Lorentz force detuning in the pulsed mode of the accelerator is limiting the maximum accelerating field of cavity at about 25 MV/m. Previous studies and tests have demonstrated that the integration of piezo actuators in the tuner can lead to the compensation of the Lorentz force detuning at field higher than 35 MV/m. Our goal is now to develop and optimize a new tuner integrating piezo actuators. The mechanical studies are now finished and fabrication is in progress. This report presents the principle of this new system, its design and reviews the cavity frequency shifts during preparation process and assesses the forces applied by the cavity on the piezo actuators. (A.C.)

  15. Multipactors in klystron cavities

    International Nuclear Information System (INIS)

    Hayashi, Kazutaka; Iyeki, Hiroshi; Kikunaga, Toshiyuki.

    1993-01-01

    A multipactor phenomenon in a klystron causes gain shortage or instability problem. Some tests using a prototype klystron input cavity revealed the microwave discharges in vacuum with magnetic field. The test results and the methods to avoid multipactors are discussed in this paper. (author)

  16. What's a Cavity?

    Science.gov (United States)

    ... and deeper over time. Cavities are also called dental caries (say: KARE-eez), and if you have a ... made up mostly of the germs that cause tooth decay. The bacteria in your mouth make acids and when plaque clings to your teeth, the acids can eat away at the outermost ...

  17. Vertical cavity laser

    DEFF Research Database (Denmark)

    2016-01-01

    The present invention provides a vertical cavity laser comprising a grating layer comprising an in-plane grating, the grating layer having a first side and having a second side opposite the first side and comprising a contiguous core grating region having a grating structure, wherein an index...

  18. Oral cavity and jaw

    International Nuclear Information System (INIS)

    Solntsev, A.M.; Koval', G.Yu.

    1984-01-01

    Radioanatome of oral cavity and jaw is described. Diseases of the teeth, jaw, large salivary glands, temporo-mandibular articulation are considered. Roentgenograms of oral cacity and jaw of healthy people are presented and analyzed as well as roentgenograms in the above-mentioned diseases

  19. Niobium superconducting cavity

    CERN Multimedia

    CERN PhotoLab

    1980-01-01

    This 5-cell superconducting cavity, made from bulk-Nb, stems from the period of general studies, not all directed towards direct use at LEP. This one is dimensioned for 1.5 GHz, the frequency used at CEBAF and also studied at Saclay (LEP RF was 352.2 MHz). See also 7908227, 8007354, 8209255, 8210054, 8312339.

  20. Superconducting elliptical cavities

    CERN Document Server

    Sekutowicz, J K

    2011-01-01

    We give a brief overview of the history, state of the art, and future for elliptical superconducting cavities. Principles of the cell shape optimization, criteria for multi-cell structures design, HOM damping schemes and other features are discussed along with examples of superconducting structures for various applications.

  1. Additive Manufactured Superconducting Cavities

    Science.gov (United States)

    Holland, Eric; Rosen, Yaniv; Woolleet, Nathan; Materise, Nicholas; Voisin, Thomas; Wang, Morris; Mireles, Jorge; Carosi, Gianpaolo; Dubois, Jonathan

    Superconducting radio frequency cavities provide an ultra-low dissipative environment, which has enabled fundamental investigations in quantum mechanics, materials properties, and the search for new particles in and beyond the standard model. However, resonator designs are constrained by limitations in conventional machining techniques. For example, current through a seam is a limiting factor in performance for many waveguide cavities. Development of highly reproducible methods for metallic parts through additive manufacturing, referred to colloquially as 3D printing\\x9D, opens the possibility for novel cavity designs which cannot be implemented through conventional methods. We present preliminary investigations of superconducting cavities made through a selective laser melting process, which compacts a granular powder via a high-power laser according to a digitally defined geometry. Initial work suggests that assuming a loss model and numerically optimizing a geometry to minimize dissipation results in modest improvements in device performance. Furthermore, a subset of titanium alloys, particularly, a titanium, aluminum, vanadium alloy (Ti - 6Al - 4V) exhibits properties indicative of a high kinetic inductance material. This work is supported by LDRD 16-SI-004.

  2. Cavity Nesting Birds

    Science.gov (United States)

    Virgil E. Scott; Keith E. Evans; David R. Patton; Charles P. Stone

    1977-01-01

    Many species of cavity-nesting birds have declined because of habitat reduction. In the eastern United States, where primeval forests are gone, purple martins depend almost entirely on man-made nesting structures (Allen and Nice 1952). The hole-nesting population of peregrine falcons disappeared with the felling of the giant trees upon which they depended (Hickey and...

  3. LEP superconducting cavity

    CERN Multimedia

    1995-01-01

    Engineers work in a clean room on one of the superconducting cavities for the upgrade to the LEP accelerator, known as LEP-2. The use of superconductors allow higher electric fields to be produced so that higher beam energies can be reached.

  4. Open microwave cavities

    Czech Academy of Sciences Publication Activity Database

    Šeba, Petr; Rotter, I.; Mueller, M.; Persson, C.; Pichugin, Konstantin N.

    2001-01-01

    Roč. 9, - (2001), s. 484-487 ISSN 1386-9477 Institutional research plan: CEZ:A02/98:Z1-010-914 Keywords : microwave cavity * resonances Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.009, year: 2001

  5. Filling a Conical Cavity

    Science.gov (United States)

    Nye, Kyle; Eslam-Panah, Azar

    2016-11-01

    Root canal treatment involves the removal of infected tissue inside the tooth's canal system and filling the space with a dense sealing agent to prevent further infection. A good root canal treatment happens when the canals are filled homogeneously and tightly down to the root apex. Such a tooth is able to provide valuable service for an entire lifetime. However, there are some examples of poorly performed root canals where the anterior and posterior routes are not filled completely. Small packets of air can be trapped in narrow access cavities when restoring with resin composites. Such teeth can cause trouble even after many years and lead the conditions like acute bone infection or abscesses. In this study, the filling of dead-end conical cavities with various liquids is reported. The first case studies included conical cavity models with different angles and lengths to visualize the filling process. In this investigation, the rate and completeness at which a variety of liquids fill the cavity were observed to find ideal conditions for the process. Then, a 3D printed model of the scaled representation of a molar with prepared post spaces was used to simulate the root canal treatment. The results of this study can be used to gain a better understanding of the restoration for endodontically treated teeth.

  6. Implosion of the small cavity and large cavity cannonball targets

    International Nuclear Information System (INIS)

    Nishihara, Katsunobu; Yamanaka, Chiyoe.

    1984-01-01

    Recent results of cannonball target implosion research are briefly reviewed with theoretical predictions for GEKKO XII experiments. The cannonball targets are classified into two types according to the cavity size ; small cavity and large cavity. The compression mechanisms of the two types are discussed. (author)

  7. Niobium superconducting rf cavity fabrication by electrohydraulic forming

    Science.gov (United States)

    Cantergiani, E.; Atieh, S.; Léaux, F.; Perez Fontenla, A. T.; Prunet, S.; Dufay-Chanat, L.; Koettig, T.; Bertinelli, F.; Capatina, O.; Favre, G.; Gerigk, F.; Jeanson, A. C.; Fuzeau, J.; Avrillaud, G.; Alleman, D.; Bonafe, J.; Marty, P.

    2016-11-01

    Superconducting rf (SRF) cavities are traditionally fabricated from superconducting material sheets or made of copper coated with superconducting material, followed by trim machining and electron-beam welding. An alternative technique to traditional shaping methods, such as deep-drawing and spinning, is electrohydraulic forming (EHF). In EHF, half-cells are obtained through ultrahigh-speed deformation of blank sheets, using shockwaves induced in water by a pulsed electrical discharge. With respect to traditional methods, such a highly dynamic process can yield interesting results in terms of effectiveness, repeatability, final shape precision, higher formability, and reduced springback. In this paper, the first results of EHF on high purity niobium are presented and discussed. The simulations performed in order to master the multiphysics phenomena of EHF and to adjust its process parameters are presented. The microstructures of niobium half-cells produced by EHF and by spinning have been compared in terms of damage created in the material during the forming operation. The damage was assessed through hardness measurements, residual resistivity ratio (RRR) measurements, and electron backscattered diffraction analyses. It was found that EHF does not worsen the damage of the material during forming and instead, some areas of the half-cell have shown lower damage compared to spinning. Moreover, EHF is particularly advantageous to reduce the forming time, preserve roughness, and to meet the final required shape accuracy.

  8. Hollow waveguide cavity ringdown spectroscopy

    Science.gov (United States)

    Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

    2012-01-01

    Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

  9. Optimization of photonic crystal cavities

    DEFF Research Database (Denmark)

    Wang, Fengwen; Sigmund, Ole

    2017-01-01

    We present optimization of photonic crystal cavities. The optimization problem is formulated to maximize the Purcell factor of a photonic crystal cavity. Both topology optimization and air-hole-based shape optimization are utilized for the design process. Numerical results demonstrate...... that the Purcell factor of the photonic crystal cavity can be significantly improved through optimization....

  10. Nuclear reactor cavity streaming shield

    International Nuclear Information System (INIS)

    Klotz, R.J.; Stephen, D.W.

    1978-01-01

    The upper portion of a nuclear reactor vessel supported in a concrete reactor cavity has a structure mounted below the top of the vessel between the outer vessel wall and the reactor cavity wall which contains hydrogenous material which will attenuate radiation streaming upward between vessel and the reactor cavity wall while preventing pressure buildup during a loss of coolant accident

  11. Energy, environmental and operation aspects of a SRF-fired fluidized bed waste-to-energy plant.

    Science.gov (United States)

    De Gisi, Sabino; Chiarelli, Agnese; Tagliente, Luca; Notarnicola, Michele

    2018-03-01

    A methodology based on the ISO 14031:2013 guideline has been developed and applied to a full-scale fluidized bed waste to energy plant (WtE) burning solid recovered fuel (SRF). With reference to 3years of operation, the data on energy and environmental performance, on raw materials consumptions such as sand and diesel fuel, accidental reasons of plant shutdown, have been acquired and analyzed. The obtained results have allowed to quantify the energy and environmental performance of the WtE plant under investigation by varying the amount and mixings of the inlet waste, available in form of thickened and fluff (similar to coriander) SRF. In terms of the energy performance, the fluidized bed technology applied to the SRF was able to guarantee an adequate production of electricity (satisfying the market demands), showing a relative flexibility with respect to the inlet waste. In terms of net energy production efficiency, the plant showed values in the range of 13.8-14.9% in line with similar installations. In terms of the environmental performance, the adoption of a cleaning system based on SNCR (Selective Non Catalitic Reduction)+semi-dry scrubbing+Fabric filter generated emissions usually well below the limits set by the EU Directive 2000/76/EC as well as the Italian Law 46/2014 (more restrictive) with reference to all the key parameters. In terms of the plant shutdown, the majority of problems focused on the combustion chamber and boiler due to the erosion of the refractory material of the furnace as well as to the breaking of the superheaters of the boiler. In contrast, the mechanical and electrical causes, along with those related to the control and instrumentation system, were of secondary importance. The sand bed de-fluidization was also among the leading causes of a frequent plant shutdown. In particular, results showed how although the SRF presents standard characteristics, the use of different mixtures may affect the number of plant shutdowns. The full

  12. Colloquium: cavity optomechanics

    CERN Multimedia

    2011-01-01

    Monday 14 November 2011, 17:00 Ecole de Physique, Auditoire Stueckelberg Université de Genève Cavity optomechanics: controlling micro mechanical oscillators with laser light Prof. Tobias Kippenberg EPFL, Lausanne Laser light can be used to cool and to control trapped ions, atoms and molecules at the quantum level. This has lead to spectacular advances such as the most precise atomic clocks. An outstanding frontier is the control with lasers of nano- and micro-mechancial systems. Recent advances in cavity optomechanics have allowed such elementary control for the first time, enabling mechanical systems to be ground state cooled leading to readout with quantum limited sensitivity and permitting to explore new device concepts resulting from radiation pressure.  

  13. Ab Initio Study of Chemical Reactions of Cold SrF and CaF Molecules with Alkali-Metal and Alkaline-Earth-Metal Atoms: The Implications for Sympathetic Cooling.

    Science.gov (United States)

    Kosicki, Maciej Bartosz; Kędziera, Dariusz; Żuchowski, Piotr Szymon

    2017-06-01

    We investigate the energetics of the atom exchange reaction in the SrF + alkali-metal atom and CaF + alkali-metal atom systems. Such reactions are possible only for collisions of SrF and CaF with the lithium atoms, while they are energetically forbidden for other alkali-metal atoms. Specifically, we focus on SrF interacting with Li, Rb, and Sr atoms and use ab initio methods to demonstrate that the SrF + Li and SrF + Sr reactions are barrierless. We present potential energy surfaces for the interaction of the SrF molecule with the Li, Rb, and Sr atoms in their energetically lowest-lying electronic spin states. The obtained potential energy surfaces are deep and exhibit profound interaction anisotropies. We predict that the collisions of SrF molecules in the rotational or Zeeman excited states most likely have a strong inelastic character. We discuss the prospects for the sympathetic cooling of SrF and CaF molecules using ultracold alkali-metal atoms.

  14. Impact of nitrogen doping of niobium superconducting cavities on the sensitivity of surface resistance to trapped magnetic flux

    Science.gov (United States)

    Gonnella, Dan; Kaufman, John; Liepe, Matthias

    2016-02-01

    Future particle accelerators such as the SLAC "Linac Coherent Light Source-II" (LCLS-II) and the proposed Cornell Energy Recovery Linac require hundreds of superconducting radio-frequency (SRF) niobium cavities operating in continuous wave mode. In order to achieve economic feasibility of projects such as these, the cavities must achieve a very high intrinsic quality factor (Q0) to keep cryogenic losses within feasible limits. To reach these high Q0's in the case of LCLS-II, nitrogen-doping of niobium cavities has been selected as the cavity preparation technique. When dealing with Q0's greater than 1 × 1010, the effects of ambient magnetic field on Q0 become significant. Here, we show that the sensitivity to RF losses from trapped magnetic field in a cavity's walls is strongly dependent on the cavity preparation. Specifically, standard electropolished and 120 °C baked cavities show a sensitivity of residual resistance from trapped magnetic flux of ˜0.6 and ˜0.8 nΩ/mG trapped, respectively, while nitrogen-doped cavities show a higher sensitivity of residual resistance from trapped magnetic flux of ˜1 to 5 nΩ/mG trapped. We show that this difference in sensitivities is directly related to the mean free path of the RF surface layer of the niobium: shorter mean free paths lead to less sensitivity of residual resistance to trapped magnetic flux in the dirty limit (ℓ ≪ ξ0), while longer mean free paths lead to lower sensitivity of residual resistance to trapped magnetic flux in the clean limit (ℓ ≫ ξ0). These experimental results are also shown to have good agreement with recent theoretical predictions for pinned vortex lines oscillating in RF fields.

  15. Leaching materials from cavities

    International Nuclear Information System (INIS)

    Hodgson, T.D.; Jordan, T.W.J.

    1980-01-01

    A material is leached from a cavity by contacting the material with a liquid and subjecting the liquid to a number of pressure cycles, each pressure cycle involving a decrease in pressure to cause boiling of the liquid, followed by a rise in pressure to inhibit the boiling. The method may include the step of heating the liquid to a temperature near to its boiling point. The material may be nuclear fuel pellets or calcium carbonate pellets. (author)

  16. Superconducting cavities for HERA

    International Nuclear Information System (INIS)

    Dwersteg, B.; Ebeling, W.; Moeller, W.D.; Renken, D.; Proch, D.; Sekutowicz, J.; Susta, J.; Tong, D.

    1988-01-01

    Superconducting 500 MHz cavities are developed to demonstrate the feasibility of upgrading the e-beam energy of the HERA storage ring. A prototype module with 2 x 4 cell resonators and appropriate fundamental and higher mode couplers has been designed at DESY and is being built by industrial firms. The design and results of RF and cryogenic measurements are reported in detail. 17 references, 10 figures, 2 tables

  17. Multi-cell superconducting structures for high energy e+ e- colliders and free electron laser linacs

    CERN Document Server

    Sekutowicz, J

    2008-01-01

    This volume, which is the first in the EuCARD Editorial Series on “Accelerator Science and Technology”, is closely combined with the most advanced particle accelerators – based on Superconducting Radio Frequency (SRF) technology. In general, SRF research includes following areas: high gradient cavities, cavity prototyping, thin film technologies, large grain and mono-crystalline niobium and niobium alloys, quenching effects in superconducting cavities, SRF injectors, photo-cathodes, beam dynamics, quality of electron beams, cryogenics, high power RF sources, low level RF controls, tuners, RF power coupling to cavities, RF test infrastructures, etc. The monograph focuses on TESLA structures used in FLASH machine and planned for XFEL and ILC experiments.

  18. Contribution of SRF, Elk-1, and myocardin to airway smooth muscle remodeling in heaves, an asthma-like disease of horses.

    Science.gov (United States)

    Chevigny, Mylène; Guérin-Montpetit, Karine; Vargas, Amandine; Lefebvre-Lavoie, Josiane; Lavoie, Jean-Pierre

    2015-07-01

    Myocyte hyperplasia and hypertrophy contribute to the increased mass of airway smooth muscle (ASM) in asthma. Serum-response factor (SRF) is a transcription factor that regulates myocyte differentiation in vitro in vascular and intestinal smooth muscles. When SRF is associated with phosphorylated (p)Elk-1, it promotes ASM proliferation while binding to myocardin (MYOCD) leading to the expression of contractile elements in these tissues. The objective of this study was therefore to characterize the expression of SRF, pElk-1, and MYOCD in ASM cells from central and peripheral airways in heaves, a spontaneously occurring asthma-like disease of horses, and in controls. Six horses with heaves and five aged-matched controls kept in the same environment were studied. Nuclear protein expression of SRF, pElk-1, and MYOCD was evaluated in peripheral airways and endobronchial biopsies obtained during disease remission and after 1 and 30 days of naturally occurring antigenic exposure using immunohistochemistry and immunofluorescence techniques. Nuclear expression of SRF (P = 0.03, remission vs. 30 days) and MYOCD (P = 0.05, controls vs. heaves at 30 days) increased in the peripheral airways of horses with heaves during disease exacerbation, while MYOCD (P = 0.04, remission vs. 30 days) decreased in the central airways of control horses. No changes were observed in the expression of pElk-1 protein in either tissue. In conclusion, SRF and its cofactor MYOCD likely contribute to the hypertrophy of peripheral ASM observed in equine asthmatic airways, while the remodeling of the central airways is more static or involves different transcription factors. Copyright © 2015 the American Physiological Society.

  19. A naturally occurring single nucleotide polymorphism in the Salmonella SPI-2 type III effector srfH/sseI controls early extraintestinal dissemination.

    Directory of Open Access Journals (Sweden)

    Joshua M Thornbrough

    Full Text Available CD18 expressing phagocytes associated with the gastro-intestinal (GI epithelium can shuttle Salmonella directly into the bloodstream within a few minutes following microbial ingestion. We have previously demonstrated that Salmonella controls the CD18 pathway to deeper tissue, manipulating the migratory properties of infected cells as an unappreciated component of its pathogenesis. We have observed that one type III effector, SrfH (also called SseI that Salmonella secretes into infected phagocytes manipulates the host protein TRIP6 to stimulate their migration. Paradoxically, SrfH was shown in another study to subvert a different host protein, IQGAP1, in a manner that inhibits the productive motility of such cells, perhaps to avoid interactions with T cells. Here, we resolve the discrepancy. We report that one naturally occurring allele of srfH promotes the migration of infected phagocytes into the bloodstream, while another naturally occurring allele that differs by only a single nucleotide polymorphism (SNP does not. This SNP determines if the protein contains an aspartic acid or a glycine residue at position 103 and may determine if SrfH binds TRIP6. SrfH Gly103 is a rare allele, but is present in the highly invasive strain Salmonella enterica serovar Typhimurium UK-1 (stands for universal killer. It is also present in the genome of the only sequenced strain belonging to the emerging pandemic Salmonella enterica serovar 4, [5],12,i:-, which is frequently associated with septicemia. Finally, we present evidence that suggests that Gifsy-2, the bacteriophage upon which srfH resides, is present in a clinical isolate of the human-specific pathogen, Salmonella enterica serovar Typhi. These observations may have interesting implications for our understanding of Salmonella pathogenesis.

  20. CHALLENGES ENCOUNTERED DURING THE PROCESSING OF THE BNL ERL 5 CELL ACCELERATING CAVITY

    Energy Technology Data Exchange (ETDEWEB)

    BURRILL,A.

    2007-06-25

    One of the key components for the Energy Recovery Linac being built by the Electron cooling group in the Collider Accelerator Department is the 5 cell accelerating cavity which is designed to accelerate 2 MeV electrons from the gun up to 15-20 MeV, allow them to make one pass through the ring and then decelerate them back down to 2 MeV prior to sending them to the dump. This cavity was designed by BNL and fabricated by AES in Medford, NY. Following fabrication it was sent to Thomas Jefferson Lab in VA for chemical processing, testing and assembly into a string assembly suitable for shipment back to BNL for integration into the ERL. The steps involved in this processing sequence will be reviewed and the deviations from processing of similar SRF cavities will be discussed. The lessons learned from this process are documented to help future projects where the scope is different from that normally encountered.

  1. Challenges Encountered during the Processing of the BNL ERL 5 Cell Accelerating Cavity

    Energy Technology Data Exchange (ETDEWEB)

    A. Burrill; I. Ben-Zvi; R. Calaga; H. Hahn; V. Litvinenko; G. T. McIntyre; P. Kneisel; J. Mammosser; J. P. Preble; C. E. Reece; R. A. Rimmer; J. Saunders

    2007-08-01

    One of the key components for the Energy Recovery Linac being built by the Electron cooling group in the Collider Accelerator Department is the 5 cell accelerating cavity which is designed to accelerate 2 MeV electrons from the gun up to 15-20 MeV, allow them to make one pass through the ring and then decelerate them back down to 2 MeV prior to sending them to the dump. This cavity was designed by BNL and fabricated by AES in Medford, NY. Following fabrication it was sent to Thomas Jefferson Lab in VA for chemical processing, testing and assembly into a string assembly suitable for shipment back to BNL and integration into the ERL. The steps involved in this processing sequence will be reviewed and the deviations from processing of similar SRF cavities will be discussed. The lessons learned from this process are documented to help future projects where the scope is different from that normally encountered.

  2. Crab cavities for linear colliders

    CERN Document Server

    Burt, G; Carter, R; Dexter, A; Tahir, I; Beard, C; Dykes, M; Goudket, P; Kalinin, A; Ma, L; McIntosh, P; Shulte, D; Jones, Roger M; Bellantoni, L; Chase, B; Church, M; Khabouline, T; Latina, A; Adolphsen, C; Li, Z; Seryi, Andrei; Xiao, L

    2008-01-01

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  3. Short Rotation Forestry (SRF in a Mediterranean Environment Under Limited Energy Inputs

    Directory of Open Access Journals (Sweden)

    Antonio Sergio De Franchi

    2010-10-01

    Full Text Available The aim of this work is comparing the two year performance (diameter, total height and mortality of twenty tree and shrub species in a semi arid environment. The research also wants to supply recommendation on the agronomic cropping techniques in areas where rainfall is the main limiting factor and water use is strictly limited. Woody biomass is gaining increasing importance for energy production in Italy. During the last five years, roughly 5000 ha of Short Rotation Forestry (SRF have been planted, mostly in northern Italy, especially using poplar clones. However, in Southern Italy, due to the poor rainfall and the lack of knowledge existing on the species to use, few groves have been established. The studied groves were set in December 2005 in a Mediterranean area where the total year rainfall is not higher than 600 mm (mostly in autumn and winter. Twenty species (Salix cinerea, Ulmus carpinifolia, Corylus avellana, Spartium junceum, Acer saccharinum, Morus alba, Saphora japonica, Eleagnus angustifolia, Fraxinus angustifolia (var oxicarpa, Sambucus nigra, Robinia pseudoacacia, Populus nigra, Albizia julibrissis, Populus alba, Salix alba, Ailanthus altissima, Alnus cordata, Ficus carica, Eucalyptus camaldulensis, Celtis australis were planted in “collection” plots and set in singular plots on single rows (3 m X 0.5 m spacing. Six species (R. pseudoacacia, P. nigra, P. alba, S. nigra, E. camaldulensis, and A. altissima were planted in eighteen random “experimental” split-plots, using single and twin rows (0.5 m spacing between plants. Plots had a rectangular plant spacing (3 m between singular and twin rows, 0.5 m on each row. Plant density was roughly 6670 cuttings ha-1 in “collection” plots with singular rows and 10950 cuttings ha-1 in “experimental” plots using single and twin rows. The expected harvest interval ranges from 2 to 5 years, depending on the first results. In the “collection” plots, the first results showed

  4. Short Rotation Forestry (SRF in a Mediterranean Environment Under Limited Energy Inputs

    Directory of Open Access Journals (Sweden)

    Stella Lovelli

    2010-12-01

    Full Text Available The aim of this work is comparing the two year performance (diameter, total height and mortality of twenty tree and shrub species in a semi arid environment. The research also wants to supply recommendation on the agronomic cropping techniques in areas where rainfall is the main limiting factor and water use is strictly limited. Woody biomass is gaining increasing importance for energy production in Italy. During the last five years, roughly 5000 ha of Short Rotation Forestry (SRF have been planted, mostly in northern Italy, especially using poplar clones. However, in Southern Italy, due to the poor rainfall and the lack of knowledge existing on the species to use, few groves have been established. The studied groves were set in December 2005 in a Mediterranean area where the total year rainfall is not higher than 600 mm (mostly in autumn and winter. Twenty species (Salix cinerea, Ulmus carpinifolia, Corylus avellana, Spartium junceum, Acer saccharinum, Morus alba, Saphora japonica, Eleagnus angustifolia, Fraxinus angustifolia (var oxicarpa, Sambucus nigra, Robinia pseudoacacia, Populus nigra, Albizia julibrissis, Populus alba, Salix alba, Ailanthus altissima, Alnus cordata, Ficus carica, Eucalyptus camaldulensis, Celtis australis were planted in “collection” plots and set in singular plots on single rows (3 m X 0.5 m spacing. Six species (R. pseudoacacia, P. nigra, P. alba, S. nigra, E. camaldulensis, and A. altissima were planted in eighteen random “experimental” split-plots, using single and twin rows (0.5 m spacing between plants. Plots had a rectangular plant spacing (3 m between singular and twin rows, 0.5 m on each row. Plant density was roughly 6670 cuttings ha-1 in “collection” plots with singular rows and 10950 cuttings ha-1 in “experimental” plots using single and twin rows. The expected harvest interval ranges from 2 to 5 years, depending on the first results. In the “collection” plots, the first results showed

  5. A Two-Level Sensorless MPPT Strategy Using SRF-PLL on a PMSG Wind Energy Conversion System

    Directory of Open Access Journals (Sweden)

    Amina Echchaachouai

    2017-01-01

    Full Text Available In this paper, a two-level sensorless Maximum Power Point Tracking (MPPT strategy is presented for a variable speed Wind Energy Conversion System (WECS. The proposed system is composed of a wind turbine, a direct-drive Permanent Magnet Synchronous Generator (PMSG and a three phase controlled rectifier connected to a DC load. The realised generator output power maximization analysis justifies the use of the Field Oriented Control (FOC giving the six Pulse Width Modulation (PWM signals to the active rectifier. The generator rotor speed and position required by the FOC and the sensorless MPPT are estimated using a Synchronous Reference Frame Phase Locked Loop (SRF-PLL. The MPPT strategy used consists of two levels, the first level is a power regulation loop and the second level is an extremum seeking bloc generating the coefficient gathering the turbine characteristics. Experimental results validated on a hardware test setup using a DSP digital board (dSPACE 1104 are presented. Figures illustrating the estimated speed and angle confirm that the SRF-PLL is able to give an estimated speed and angle which closely follow the real ones. Also, the power at the DC load and the power at the generator output indicate that the MPPT gives optimum extracted power. Finally, other results show the effectiveness of the adopted approach in real time applications.

  6. ISR RF cavities

    CERN Multimedia

    1983-01-01

    In each ISR ring the radiofrequency cavities were installed in one 9 m long straight section. The RF system of the ISR had the main purpose to stack buckets of particles (most of the time protons)coming from the CPS and also to accelerate the stacked beam. The installed RF power per ring was 18 kW giving a peak accelerating voltage of 20 kV. The system had a very fine regulation feature allowing to lower the voltage down to 75 V in a smooth and well controlled fashion.

  7. RF, Thermal and Structural Analysis of the 201.25 MHz Muon Ionization Cooling Cavity

    International Nuclear Information System (INIS)

    Virostek, S.; Li, D.

    2005-01-01

    A finite element analysis has been carried out to characterize the RF, thermal and structural behavior of the prototype 201.25 MHz cavity for a muon ionization cooling channel. A single ANSYS model has been developed to perform all of the calculations in a multi-step process. The high-gradient closed-cell cavity is currently being fabricated for the MICE (international Muon Ionization Cooling Experiment) and MUCOOL experiments. The 1200 mm diameter cavity is constructed of 6 mm thick copper sheet and incorporates a rounded pillbox-like profile with an open beam iris terminated by 420 mm diameter, 0.38 mm thick curved beryllium foils. Tuning is accomplished through elastic deformation of the cavity, and cooling is provided by external water passages. Details of the analysis methodology will be presented including a description of the ANSYS macro that computes the heat loads from the RF solution and applies them directly to the thermal model. The process and results of a calculation to determine the resulting frequency shift due to thermal and structural distortion of the cavity will also be presented

  8. Characterization of Nb Superconducting Radio Frequency Cavities Based On In-Situ STEM And EELS

    Science.gov (United States)

    Tao, Runzhe

    Niobium, a 4d transition metal, has the highest superconducting transition temperature (Tc=9.2K) of any elemental superconductor as type II superconductor with coherent length, sigma approximately that of the penetration length, lambda. Pure niobium is grey in color and very soft, which makes this metal easily fabricable into different shapes for superconducting radio- frequency (SRF) cavities. Such cavities are used in some modern accelerators (SNS, CEBAF, XFEL), and are intended for usage in the next generation of particle accelerators, such as ILC. Since the crucial part of the cavities is top 100 nm of Nb near the inner cavity surface, considering the penetration depth is around 40 nm, it has attracted more and more attention in improving the surface process for optimizing the performance of the cavities. Nowadays, the main treatment of the Nb surface includes electro polishing (EP), buffered chemical polishing (BCP), high temperature baking (800 °C, 1000 °C and 1200 °C) and mild baking (120 °C). Firstly, the two half cells are welded together and the weld line is quite rough; there exists a lot of visible pits and defects on the inner shell of cavities. In this Ph.D. thesis, novel techniques in a scanning transmission electron microscope (STEM) that can be used to analyze the atomic scale structure-property relationship, both at room tem- perature and high/LN 2 temperature, are explored. Specifically, by using correlated Z-contrast imaging and electron energy loss spectrum (EELS), the structure, composition and bonding can be characterized directly on the atomic scale, also, light atoms, like H, O and C, are visible in ABF images. For the examining the defect behavior on the cavity surface, heating and cold stages are involved to simulate the baking treatment and low-temperature environments. These studies will serve as an important reference for qualifying different surface treatments to further improve SRF cavities' performance. The experimental results

  9. Analysis of a grid window structure for RF cavities in a Muon cooling channel

    International Nuclear Information System (INIS)

    Ladran, A.; Li, D.; Moretti, A.; Rimmer, R.; Staples, J.; Virostek, S.; Zisman, M.

    2003-01-01

    We report on the electromagnetic and thermal analysis of a grid window structure for high gradient, low frequency RF cavities. Windows may be utilized to close the beam iris and increase shunt impedance of closed-cell RF cavities. This work complements previous work presented for windows made of solid beryllium foil. An electromagnetic and thermal analysis of the thin wall tubes in a grid pattern was conducted using both MAFIA4 and ANSYS finite element analyses. The results from both codes agreed well for a variety of grid configurations and spacing. The grid configuration where the crossing tubes touched was found to have acceptable E-Fields and H-Fields performance. The thermal profiles for the grid will also be shown to determine a viable cooling profile

  10. SQUID based cryogenic current comparator for measurements of the dark current of superconducting cavities

    Energy Technology Data Exchange (ETDEWEB)

    Vodel, W.; Nietzsche, S.; Neubert, R.; Nawrodt, R. [Friedrich Schiller Univ. Jena (Germany); Peters, A. [GSI Darmstadt (Germany); Knaack, K.; Wendt, M.; Wittenburg, K. [DESY Hamburg (Germany)

    2005-07-01

    The linear accelerator technology, based on super-conducting L-band (1.3 GHz) is currently under study at DESY (Hamburg, Germany). The two 10 km long main Linacs will be equipped with a total of nearly 20.000 cavities. The dark current due to the emission of electrons in these high gradient field super-conducting cavities is an unwanted particle source. A newly high performance SQUID based measurement system for detecting dark currents is proposed. It makes use of the Cryogenic Current Comparator principle and senses dark currents in the pA range with a measurement bandwidth of up to 70 kHz. The use of a cryogenic current comparator as dark current sensor has some important advantages: -) the measurement of the absolute value of the dark current, -) the non-dependence on the electron trajectories, -) the accurate absolute calibration with an additional wire loop, and -) extremely high resolution.

  11. Oral cavity eumycetoma

    Directory of Open Access Journals (Sweden)

    Gisele Alborghetti Nai

    2011-06-01

    Full Text Available Mycetoma is a pathological process in which eumycotic (fungal or actinomycotic causative agents from exogenous source produce grains. It is a localized chronic and deforming infectious disease of subcutaneous tissue, skin and bones. We report the first case of eumycetoma of the oral cavity in world literature. CASE REPORT: A 43-year-old male patient, complaining of swelling and fistula in the hard palate. On examination, swelling of the anterior and middle hard palate, with fistula draining a dark liquid was observed. The panoramic radiograph showed extensive radiolucent area involving the region of teeth 21-26 and the computerized tomography showed communication with the nasal cavity, suggesting the diagnosis of periapical cyst. Surgery was performed to remove the lesion. Histopathological examination revealed purulent material with characteristic grain. Gram staining for bacteria was negative and Grocott-Gomori staining for the detection of fungi was positive, concluding the diagnosis of eumycetoma. The patient was treated with ketoconazole for nine months, and was considered cured at the end of treatment. CONCLUSION: Histopathological examination, using histochemical staining, and direct microscopic grains examination can provide the distinction between eumycetoma and actinomycetoma accurately.

  12. Cryostat for TRISTAN superconducting cavity

    International Nuclear Information System (INIS)

    Mitsunobu, S.; Furuya, T.; Hara, K.

    1990-01-01

    Superconducting cavities generate rather high heat load of hundreds watts in one cryostat and have high sensitivity for pressure. We adopted usual pool-boiling type cooling for its stable pressure operation. Two 5-cell Nb cavities were installed in one flange type cryostat. Tuning mechanics actuated by a pulse-motor and a Piezo-electric element are set at outside of vacuum end flange. The design and performance of the cryostat for TRISTAN superconducting cavities are described. (author)

  13. Superconducting Radio-Frequency Cavities

    Science.gov (United States)

    Padamsee, Hasan S.

    2014-10-01

    Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

  14. Model for initiation of quality factor degradation at high accelerating fields in superconducting radio-frequency cavities

    International Nuclear Information System (INIS)

    Dzyuba, A; Romanenko, A; Cooley, L D

    2010-01-01

    A model for the onset of the reduction in superconducting radio-frequency (SRF) cavity quality factor, the so-called Q-drop, at high accelerating electric fields is presented. Since magnetic fields at the cavity equator are tied to accelerating electric fields by a simple geometric factor, the onset of magnetic flux penetration determines the onset of Q-drop. We consider breakdown of the surface barrier at triangular grooves to predict the magnetic field of first flux penetration H pen . Such defects were argued to be the worst case by Buzdin and Daumens (1998 Physica C 294 257), whose approach, moreover, incorporates both the geometry of the groove and local contamination via the Ginzburg-Landau parameter κ. Since previous Q-drop models focused on either topography or contamination alone, the proposed model allows new comparisons of one effect in relation to the other. The model predicts equivalent reduction of H pen when either roughness or contamination were varied alone, so smooth but dirty surfaces limit cavity performance about as much as rough but clean surfaces do. Still lower H pen was predicted when both effects were combined, i.e. contamination should exacerbate the negative effects of roughness and vice versa. To test the model with actual data, coupons were prepared by buffered chemical polishing and electropolishing, and stylus profilometry was used to obtain distributions of angles. From these data, curves for surface resistance generated by simple flux flow as a function of magnetic field were generated by integrating over the distribution of angles for reasonable values of κ. This showed that combined effects of roughness and contamination indeed reduce the Q-drop onset field by ∼ 20%, and that contamination contributes to Q-drop as much as roughness. The latter point may be overlooked by SRF cavity research, since access to the cavity interior by spectroscopy tools is very difficult, whereas optical images have become commonplace. The model

  15. Model for initiation of quality factor degradation at high accelerating fields in superconducting radio-frequency cavities

    Science.gov (United States)

    Dzyuba, A.; Romanenko, A.; Cooley, L. D.

    2010-12-01

    A model for the onset of the reduction in superconducting radio-frequency (SRF) cavity quality factor, the so-called Q-drop, at high accelerating electric fields is presented. Since magnetic fields at the cavity equator are tied to accelerating electric fields by a simple geometric factor, the onset of magnetic flux penetration determines the onset of Q-drop. We consider breakdown of the surface barrier at triangular grooves to predict the magnetic field of first flux penetration Hpen. Such defects were argued to be the worst case by Buzdin and Daumens (1998 Physica C 294 257), whose approach, moreover, incorporates both the geometry of the groove and local contamination via the Ginzburg-Landau parameter κ. Since previous Q-drop models focused on either topography or contamination alone, the proposed model allows new comparisons of one effect in relation to the other. The model predicts equivalent reduction of Hpen when either roughness or contamination were varied alone, so smooth but dirty surfaces limit cavity performance about as much as rough but clean surfaces do. Still lower Hpen was predicted when both effects were combined, i.e. contamination should exacerbate the negative effects of roughness and vice versa. To test the model with actual data, coupons were prepared by buffered chemical polishing and electropolishing, and stylus profilometry was used to obtain distributions of angles. From these data, curves for surface resistance generated by simple flux flow as a function of magnetic field were generated by integrating over the distribution of angles for reasonable values of κ. This showed that combined effects of roughness and contamination indeed reduce the Q-drop onset field by ~ 20%, and that contamination contributes to Q-drop as much as roughness. The latter point may be overlooked by SRF cavity research, since access to the cavity interior by spectroscopy tools is very difficult, whereas optical images have become commonplace. The model was

  16. CEBAF: Accelerating cavities look good

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1990-09-15

    The first assembled pairs of superconducting accelerating cavities from German supplier Interatom for the Continuous Electron Beam Accelerator Facility, Newport News, Virginia, have exceeded performance specifications.

  17. CEBAF: Accelerating cavities look good

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    The first assembled pairs of superconducting accelerating cavities from German supplier Interatom for the Continuous Electron Beam Accelerator Facility, Newport News, Virginia, have exceeded performance specifications

  18. Prospects for a soft x-ray FEL powered by a relativistic-klystron high-gradient accelerator (RK-HGA)

    International Nuclear Information System (INIS)

    Shay, H.D.; Barletta, W.A.; Yu, S.S.; Schlueter, R.; Deis, G.A.

    1989-01-01

    We present here the concept of x-ray FELs using high gain, single-pass amplifiers with electron beams accelerated in high gradient structures powered by relativistic klystrons. Other authors have also considered x-ray FELs; the unique aspect of this paper is the use of high gradient acceleration. One of the authors has previously presented preliminary studies on this concept. The intent in this paper is to display the results of a top level design study on a high gain FEL, to present its sensitivity to a variety of fabrication and tuning errors, to discuss several mechanisms for increasing gain yet more, and to present explicitly the output characteristics of such an FEL. The philosophy of the design study is to find a plausible operating point which employs existing or nearly existing state-of-the-art technologies while minimizing the accelerator and wiggler lengths. The notion is to distribute the technical risk as evenly as possible over the several technologies so that each must advance only slightly in order to make this design feasible. This study entailed no systematic investigation of possible costs so that, for example, the sole criterion for balancing the trade-off between beam energy and wiggler length is that the two components have comparable lengths. 20 refs., 10 figs., 1 tab

  19. Locally expressed IGF1 propeptide improves mouse heart function in induced dilated cardiomyopathy by blocking myocardial fibrosis and SRF-dependent CTGF induction

    Directory of Open Access Journals (Sweden)

    Melissa Touvron

    2012-07-01

    Cardiac fibrosis is critically involved in the adverse remodeling accompanying dilated cardiomyopathies (DCMs, which leads to cardiac dysfunction and heart failure (HF. Connective tissue growth factor (CTGF, a profibrotic cytokine, plays a key role in this deleterious process. Some beneficial effects of IGF1 on cardiomyopathy have been described, but its potential role in improving DCM is less well characterized. We investigated the consequences of expressing a cardiac-specific transgene encoding locally acting IGF1 propeptide (muscle-produced IGF1; mIGF1 on disease progression in a mouse model of DCM [cardiac-specific and inducible serum response factor (SRF gene disruption] that mimics some forms of human DCM. Cardiac-specific mIGF1 expression substantially extended the lifespan of SRF mutant mice, markedly improved cardiac functions, and delayed both DCM and HF. These protective effects were accompanied by an overall improvement in cardiomyocyte architecture and a massive reduction of myocardial fibrosis with a concomitant amelioration of inflammation. At least some of the beneficial effects of mIGF1 transgene expression were due to mIGF1 counteracting the strong increase in CTGF expression within cardiomyocytes caused by SRF deficiency, resulting in the blockade of fibroblast proliferation and related myocardial fibrosis. These findings demonstrate that SRF plays a key role in the modulation of cardiac fibrosis through repression of cardiomyocyte CTGF expression in a paracrine fashion. They also explain how impaired SRF function observed in human HF promotes fibrosis and adverse cardiac remodeling. Locally acting mIGF1 efficiently protects the myocardium from these adverse processes, and might thus represent a therapeutic avenue to counter DCM.

  20. Screening and ranking framework (SRF) for geologic CO2 storagesite selection on the basis of HSE risk

    Energy Technology Data Exchange (ETDEWEB)

    Oldenburg, Curtis M.

    2006-11-27

    A screening and ranking framework (SRF) has been developedto evaluate potential geologic carbon dioxide (CO2) storage sites on thebasis of health, safety, and environmental (HSE) risk arising from CO2leakage. The approach is based on the assumption that CO2 leakage risk isdependent on three basic characteristics of a geologic CO2 storage site:(1) the potential for primary containment by the target formation; (2)the potential for secondary containment if the primary formation leaks;and (3) the potential for attenuation and dispersion of leaking CO2 ifthe primary formation leaks and secondary containment fails. Theframework is implemented in a spreadsheet in which users enter numericalscores representing expert opinions or published information along withestimates of uncertainty. Applications to three sites in Californiademonstrate the approach. Refinements and extensions are possible throughthe use of more detailed data or model results in place of propertyproxies.